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Thymic regulatory T cells
Autoimmunity Reviews 4 (2005) 579 – 586 www.elsevier.com/locate/autrev
Thymic regulatory T cells Enrico Maggi*, Lorenzo Cosmi, Francesco Liotta, Paola Romagnani, Sergio Romagnani, Francesco Annunziato Center of Research, Transfer, High Education dMCIDNENT T, University of Florence, Firenze, Italy Available online 16 May 2005
Abstract Several types of T regulatory (Treg) cells have been described in both mice and humans, including natural or professional (CD4+CD25+ T cells) and adaptive (Th3 and Tr1 cells) Treg cells. The former develops in the thymus and results in an endogeneous long-lived population of self-antigen-specific T cells in the periphery poised to prevent potentially autoimmune reactions. The second subset develops as a consequence of activation of mature T cells under particular conditions of suboptimal antigen exposure and/or costimulation. Natural Treg cells are positively selected in the cortex through their TCR interactions with self-peptides presented by thymic stromal cells. It is likely that this high-affinity recognition results in signals rendering them anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. Recently, small subsets of CD4+CD25+ and of CD8+CD25+ cells sharing similar characteristics have been detected in human fetal and post-natal thymuses. Both CD4+CD25+ and CD8+CD25+ human thymocytes express Foxp3 and GITR mRNA, as well as surface CCR8 and TNFR2 and cytoplasmic CTLA-4 proteins, which are common features of mature Treg cells. Following activation they do not proliferate or produce cytokines, but express surface CTLA-4 and TGF-h1. They suppress the proliferation of autologous CD4+CD25 thymocytes to allogeneic stimulation by a contact-dependent mechanism related to the combined action of surface CTLA-4 and TGF-h leading to the inhibition of the IL-2R a chain on target T cells. Lastly, both CD4+CD25+ and CD8+CD25+ Treg thymocytes exert strong suppressive activity on Th1, but much lower on Th2 cells, since these latter may escape from suppression via their ability to respond to growth factors other than IL-2. Treg cells that develop in, and emerge from, the thymus are certainly responsible for the maintenance of selftolerance and prevention of autoimmune disorders. The result that Th1 cells are highly susceptible to the suppressive activity of Treg thymocytes is consistent with the important role of these cells in protecting against the Th1-mediated immune response to autoantigens. D 2005 Elsevier B.V. All rights reserved. Keywords: Autoimmunity; CD4+CD25 +/CD8+CD25+ T-regulatory cells; Foxp3; Immunoregulation; Thymus
* Corresponding author. Centro di Ricerca, Trasferimento e Alta Formazione dMCIDNENTT, Universita` di Firenze, Policlinico di Careggi, Viale Morgagni, 85, 50134 Firenze (I), Italy. Tel.: +39 55 4296429; fax: +39 55 4296449. E-mail address: [email protected] (E. Maggi). 1568-9972/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.autrev.2005.04.010
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1. Introduction Autoimmune disorders are characterized by a breakdown in the mechanisms of tolerance to selfantigens. The negative selection of autoreactive thymocytes is the first self-tolerance mechanism occurring in the thymus but, even if it is high efficient, a number of self-reactive cells overcome the selection barrier [1]. Thus, autoreactive T cells may be activated by peripheral tissues- or self-mimicking exogeneous antigens leading to subsequent autoaggression [2]. Even though circulating autoreactive T cells are present in all individuals, the prevalence of autoimmune disorders affects only a minimal proportions of subjects, suggesting that mechanisms of peripheral tolerance operate to silence potentially pathogenetic T cells. In the last decade there has been an intense focus on the role of Treg cell in controlling immune responses and several types of Treg cells have been identified in both mice and humans [3]. They include cross regulatory Th1 and Th2 cells, CD4+ T cells producing soluble TGF-h 1 (Th3 cells), which are able to inhibit the outcome of some autoimmune disorders [4,5] and CD4+ T regulatory 1 (Tr1) cells producing high levels of IL-10 and inhibiting some Tcell responses in vivo [6]. Also CD8+CD28 cells, natural killer T (NKT) cells, g y T cells have been included into Treg cell family [7–9]. Finally, another Treg cell subset, characterized by the constitutive high expression of the IL-2R a chain (CD25high), which is called as the CD4+CD25+ Treg population, has been demonstrated in the thymus and peripheral blood (PB) from both mice and humans [10]. Neonatally thymectomized mice, which are deficient in this population of T cells, develop multiorgan autoimmune disease, which can be overcome by the adoptive transfer of CD4+CD25+ cells from normal mice, thus suggesting a central role of these cells in self-tolerance [2]. In addition, adult thymectomy and subsequent sublethal X-irradiation produce thyroiditis and type 1 diabetes in selected strains of mice [2,3]. There is now a general consensus that the thymic Treg cells are involved in active mechanism of peripheral tolerance of autoreactive T cells that have escaped thymic selection [2–5]. Based on extensive data in mouse models, two subsets of Treg cells have been proposed which differ
in terms of specificity and effector mechanisms: the natural (namely the CD4+CD25+ Treg cells) regulatory cells, also defined bprofessional TregQ, develop in the thymus and result in an endogeneous long-lived population of self-antigen-specific T cells in the periphery poised to prevent potentially autoimmune reactions. The second subset namely badaptive regulatory cellsQ (Tr1, Th3 and other cells) develops as a consequence of activation of mature T cells under particular conditions of sub-optimal antigen exposure and/or costimulation [11]. In this article, we will analyse the recent progress of developmental and functional features of naturally regulatory CD25+ thymocytes in mouse as in man.
2. Origin and development of Treg thymocytes Thymus produces the majority of CD25+ CD4+ Treg cells as a functionally mature T-cell subpopulation, which appears to be a distinct cellular lineage similar to circulating Treg cells. Since adoptive transfer of mature thymocytes, depleted of CD25+ T cells, induced several autoimmune diseases in syngeneic T-cell-deficient mice, it has been suggested that the normal thymus is continuously producing self-reactive CD4+ effector T cells as well as selfreactive natural Treg cells able to suppress them. This activity has been defined as the third function of the thymus [12]. Natural Treg cells develop in the thymus during the early stages of fetal and neonatal T-cell development. In mouse they are polyclonal and potentially able to recognize various self-antigens. However, the cellular basis of their maturation, the role of antigen presentation, the diversity of TCR usages and interactions with thymic microenvironment are at present unclear. By using a double transgenic mouse system, it has been shown that antigen-specific Treg cells seem to develop as a consequence of high-affinity antigen recognition. It is not known why some thymocytes escape negative selection and differentiated into Treg cells [13]. It has been proposed that they recognize tissue antigens selectively expressed by dislandsT of medullary epithelial cells, leading to a localized strong Treg cell response. Several results pointed to thymic medulla as the site for selection of CD4+CD25+ T cells in mouse, even though the
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regulatory phenotype appeared only when cells have reached the single-positive state, which is late in the selection process [13]. Other studies pointed to thymic cortex as the site for positive selection of CD4+CD25+ Treg cells, prevalently based on the expression of MHC class II by thymic cortical epithelial cells [14]. Accordingly, it has been shown that Treg cells are positively selected through their TCR affinity interactions with self-peptides presented on MHC class II molecules by thymic stromal cells. Thereafter, some data indicate that these cells are negatively selected in the medulla and deleted, even though they are less sensitive than their CD25-counterparts to agonist-induced clonal deletion [15]. Thus, Treg cell selection looks like the selection processes of other thymocytes, the only difference being in the avidity of interactions. It has been suggested that a special range of avidity results in both selection of Treg cells and the delivery of some signals leading these cells anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. It has been proposed that this protective molecule may be the glucocorticoidinduced TNF receptor (GITR) which displays an anti-apoptotic activity [16]. The presence in human fetal and post-natal thymus of subsets of mature CD4+ or CD8+ thymocytes expressing high levels of CD25 and displaying the same features of circulating CD4+CD25high regulatory cells has been recently shown [17–20]. No conclusive data, however, have been achieved on whether Treg cells follow a developmental pathway as a separate lineage or whether they are generated by differences in signalling during TCR selection. It has been shown that in human fetal thymus the CD25 molecule is acquired at the 13–17 weeks of gestation, at the CD1a+ stage during the acquisition of CD27 expression by CD4+CD8+ double-positive thymocytes. Moreover, the first CD8+CD25+ cells are found in the fetus in the subsequent CD1a+CD27+ stage. Finally, in the most mature CD1a CD27+ stage only CD4+CD8+ double-positive and CD4 single-positive thymocytes express high levels of CD25, while a small proportion of CD8 single-positive cells shows lower CD25 expression [19]. The molecular signals initiating this lineage decision remain to be defined, even though they may be linked to the strength of TCR signalling and/or to repertoire of self-peptides
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presented. According to some authors, upon exit from the thymus Treg cells enter into the circulation as naı¨ve CD45RA+GITR T cells, indeed they are able to suppress proliferation of polyclonally activated effector cells but still lack the capacity to react, or suppress responses, against autoantigens [19]. This occurs upon the transition within the fetal secondary lymphoid organs, where they acquire a more memorylike phenotype. However, it cannot be excluded that some conventional CD4+CD25 Treg cells are converted to CD4+CD25+ Treg in the periphery [21]. As a result, activated Treg cells express CD69, GITR and CD45RO and are able to suppress a broad range of response, namely due to autoreactive T effector cells escaping from thymic selections.
3. Phenotypic profile of Treg thymocytes Mouse natural Treg cells constitutively express a variety of cell surface molecules such as CD25high, CD45ROlow, CD62L, CD103, GITR and CTLA-4. Neutralising anti-GITR antibody is able to block Treg suppression in vitro and to induce autoimmune disorders in vivo by increasing proliferation of Treg cells through transduction of a costimulatory signal, and rendering effector T cells resistant to suppressive activity of Treg cells [22]. Also Neutropilin-1, a semaphoring III receptor molecule initially described to be an essential component of the immunological synapse, is highly expressed on natural Treg cells and downregulated upon their activation [23]. A deeper understanding of the developmental processes of natural Treg cells has been achieved also with the Foxp3 gene. It has been recently shown that such gene, encoding a forkhead/winged-helix family transcriptional repressor, is predominantly expressed in Treg cells in the thymus and periphery in mouse as in man [24]. The transfection of naı¨ve T cells with Foxp3 mRNA makes them anergic and suppressive resembling the phenotype and functional features of Treg cells. Adoptive transfer of these cells is able to prevent autoimmune disorders in vivo. Foxp3/FOXP3 may be considered a master regulatory gene for celllineage commitment and developmental differentiation for Treg cells from thymus and periphery. This gene is mutated in the mouse strain scurfy and in
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humans suffering from immune dysregulation polyendocrinopathy enteropathathy, X-linked syndrome (IPEX) [24]. Phenotypic profile of human Treg cells in the thymus is very similar to that described in mouse. CD4+CD25+ human Treg cells in post-natal thymus constitutively express Foxp3 and GITR mRNA [20], as well as surface TNF receptor 2 (TNFR2), and cytoplasmic CTLA-4 proteins [18]. More importantly, virtually all cells express on their surface CTLA-4 and the majority of them also membrane TGF (mTGF)-h 1 if stimulated with anti-CD3 plus anti-CD28 mAbs [18]. mRNA expression as well as surface analysis has revealed that the chemokine receptor CCR8 is constitutively expressed by CD4+CD25+ thymocytes, indeed the CCR8-ligand, I-309/CCL1 selectively attract these cells [18]. Interestingly, it was found that the CD4+CD25+ thymocytes primarily localize in the medulla, mainly in perivascular areas of the fibrous septa where epithelial cells and macrophages produce I-309/CCL1. It may be suggested that CCR8–CCL1 interaction can be involved in the spread of mature CD4+CD25+ into circulation [18]. A further subset of human regulatory thymocytes being CD8+CD25+ cells has been recently described [20]. The CD8+CD25+ thymocytes share similar phenotypic characteristics with CD4+CD25+ thymocytes, since they may be detected in the same areas of human thymus and, more importantly, they constitutively express Foxp3 and GITR mRNA. CD8+CD25+ thymocytes express both surface and cytoplasmic markers of CD4+CD25+ thymocytes whereas, differently from CD8+CD25+ effector T cells, they did not exhibit the presence of either perforin or granzyme A. Following polyclonal stimulation, CD8+CD25+ thymocytes do not produce any cytokine, but express both CTLA-4 and TGF-h 1 on their surface [20]. The physiological meaning of CD8+CD25+ Treg thymocytes is presently unclear. As previously reported, it has been suggested that CD4+CD25+ thymocytes might be educated during the selection steps to recognize self-antigens that are presented on MHC class II molecules by stromal cells in a process that is known as baltered negative selectionQ, after which they migrate directly to peripheral lymphoid tissues [13–15]. Similar explanation might be provided for CD8+CD25+ thymocytes with the only difference that these cells are educated to recognize self-antigens
that are presented on MHC class I molecules by cells present in the thymic microenvironment. After their migration to the peripheral lymphoid tissue, CD8+CD25+ Treg cells may be involved in the regulation of T-cell responses directed against viruses and transformed cells, which are usually exploited by cytotoxic CD8+ T lymphocytes. Lastly, the enrichment of CD25+ thymocytes by sorting procedure results in the clear isolation of different thymocyte subsets. In particular, based on the CD4 and CD8 expression, we were able to identify another CD25+ T-cell population (namely CD4+CD8+CD25+) which showed some features of regulatory cells. They constitutively expressed Foxp3 mRNA and were also able to suppress the proliferation of autologous CD4+CD25 thymocytes. However, it is not clear if this new subset can be related to the model described above in the mouse (Liotta F. et al., manuscript in preparation). In the fetal thymus CD4+CD25+ T cells display surface features similar to that reported of post-natal thymocytes: expression of GITR, CD122 and intracellular CTLA-4, in contrast with low expression of CD127. Also CD8+CD25+ thymocytes developed in the fetal thymus share many of characteristics with their CD4+ counterparts, as well as with the CD8+CD25+ Treg cells found in post-natal thymus. Of note, CD25+ fetal thymocytes have the potential to suppress proliferative response of autologous CD25 T cells as mature natural Treg cells [19].
4. Functional features of Treg thymocytes and mechanisms of suppression The main feature of CD25+ Treg cell subsets is their ability to downregulate immune responses. They are able to inhibit several cells involved in both innate and adaptive immune mechanisms. CD4+CD25+ Treg cells require TCR triggering, and probably IL2, to exert their suppressive effects, which are not specific towards bystander cells [25]. In mice Treg cells are anergic in vitro and do not produce IL-2 in response to conventional stimuli. However, this anergy can be overcome by high doses of IL-2, or anti-CD28 costimulus, or the use of mature DC. In vivo Treg cell anergy is rarely found and they appear to have a high turnover [26].
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Similarly to mouse Treg cells, human CD4+CD25+ and CD8+CD25+ regulatory thymocytes from both fetal and post-natal thymus show poor, if any, proliferation in response to mitogenic and mixed lymphocyte culture (MLC) stimulation and suppressed in a dose-dependent fashion the proliferative response to allogeneic stimulation of autologous CD4+CD25 thymocytes. These cells do not produce IL-2, IL-4, IL-5, IL-13, IFN-g , and only a few of them produced IL-10, upon polyclonal stimulation [18,20]. Even though the immunoregulation is the main feature of Treg cells, the fine mechanisms of suppression remain elusive. There is a general consensus that they act through a cell-to-cell contact mechanism without any effect by soluble factors produced by them or by target T cells [18,20,27]. The cell-to-cell contact mechanism involved in the suppressive activity of Treg cells has yet to be clarified. Recently, it has been shown that Treg cells may act as an IL-2 sink, depriving autoreactive T cells of autocrine IL-2 [28]. Other mechanisms include CTLA-4, an inhibitory molecule highly expressed by Treg cells. CTLA-4 has been recently shown to trigger the induction of indoleamine 2,3-dioxygenase (IDO) by DC, which catalyzes the tryptophan conversion into kinurenins, molecules showing immunosuppressive effects on several cells [29]. Some authors have also shown that Treg cells are able to downregulate the expression of costimuli (namely CD80, CD86) on DC, thus modifying their APC capacity. It has also been suggested that the engagement of CD80 and, to a lesser extent, of CD86 on the responder T cells was responsible for the negative signal given by Treg cells [30]. In human Treg thymocytes we found that the suppressive activity was partially but consistently inhibited by neutralizing antibodies towards CTLA4, TGF-h1, or TGF-h1R [18,20]. More importantly, such a suppressive activity was completely abolished by a mix of anti-CTLA-4 and anti-TGF-h1 mAbs, thus indicating that these molecules are both involved in the suppressive activity. This finding is not fully consistent with those studies performed so far by using PB CD4+CD25+ T cells, which failed to demonstrate any impairment of suppression with antiCTLA-4 or anti-TGF-h Abs [17,31,32]. This discrepancy may be due to either the heterogeneity of PB in comparison with thymus-derived CD4+CD25+ T
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cells, or to the different assays used to assess the suppressive activity. However, it has been recently shown that the suppressive activity of CD4+CD25+ murine T cells was abolished by the neutralization of TGF-h1 and that activated CD4+CD25+ T cells expressed high and persistent levels of membrane TGFh1 [33–35]. Of note, recent studies on human cells clearly showed the crucial role of TGF-h1 in the induction of the regulatory phenotype in CD4+ CD25 cells [36–38]. As previously reported, the role of CTLA-4 in the regulatory activity of murine CD4+CD25+ T cells has been clearly demonstrated in vivo. Since CTLA-4 engagement has been found to enhance the secretion of TGF-h [39], it is reasonable to explain why in our study a complete inhibition of the suppressive activity exerted by activated human Treg thymocytes could be achieved only with the contemporaneous neutralization of both CTLA-4 and TGF-h1. The results obtained by using the highly homogeneous human CD8+ or CD4+CD25+ Treg thymocyte populations provided new insights in the understanding the mechanisms by which Treg cells suppress the proliferative response of stimulated CD4+CD25 cells. CD4+CD25 cells in the presence of CD25+ regulatory thymocytes were unable to express the IL2R a chain and, therefore, became unresponsive to IL2. Moreover, the inability of effector T cells to proliferate was not affected by the addition of exogenous IL-2, but it was overcome by the addition of IL-15, a T-cell stimulatory cytokine that does not share the high-affinity IL-2R a chain [18]. These findings are consistent with a study, showing that suppression of IL-2-induced human T-cell proliferation and phosphorylation of STAT3 and STAT5 by TGF-h1 may be completely overcome by treating T cells with IL-15 [40]. More recently, we asked whether human Treg thymocytes exerted different suppressive activity on Th1 or Th2 polarized effectors. T-cell clones were generated from CD25+ thymocytes, (both CD4+ and CD8+) and their suppressive activity was evaluated on Th1 or Th2 T-cell clones derived from autologous CD4+CD25 thymocytes [41]. The results indicate that the proliferation of Th1 clones was completely suppressed by both CD4+ and CD8+ autologous Treg cells, whereas the same Treg cells exhibited much lower suppressive activity on Th2 clones. This
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difference was due to the ability of Th2 cells to produce cytokines that allow them to proliferate even in the absence of responsiveness to IL-2. Indeed, the suppressive activity of CD25+ thymocytes on Th2 clones was enhanced by neutralization in culture of IL-4, whereas it was completely blocked by the addition of recombinant IL-4, IL-7, IL-9, and IL-15. By contrast, the proliferation of Th1 cells was only restored by the administration in culture of IL-15. Accordingly, Th2 clones expressed significantly higher levels of IL-4R and IL-9R mRNA than Th1 clones, whereas the expression on Th1 and Th2 cells of IL-2R, IL-7R, and IL-15R was comparable [41]. These data suggest that, although Treg cells regulate both Th1 and Th2 responses downregulating the expression of IL-2R in effector T cells, Th2 cells may partially escape to this suppressive activity via their ability to respond to grow factors different from IL-2 such as IL-4, IL-7 and IL-9. In particular IL-4, produced by Th2 cells and acting in an autocrine fashion, can, at least in part, bypass the regulatory effects exerted by CD4+CD25+ Treg cells. Accordingly, CD4+CD25 cells from NFATc2 / c3 / double knockout mice, which develop massive lymphadenopathy, splenomegaly and strong increase in serum IgE and IgG1 levels, caused by preferential differentiation of naive T cells into Th2 cells, are unresponsive to CD4+CD25+ Treg suppression, even in the absence of exogeneous IL-4 [42]. Finally, these data are consistent with the observation that depletion in mice of CD4+CD25+ T cells prevents antigen-induced Th2 differentiation by increasing the differentiation of Th1 cells [43]. The demonstration that both CD4+CD25+ and CD8+CD25+ Treg thymocytes can exert strong suppressive activity on Th1, but much lower on Th2, cells is of great potential interest. In fact, while autoimmune diseases are mainly associated with Th1-mediated immune responses [2,4,6], the Th2 cells are more rarely detectable in tissues affected by autoimmune disorders and their cytokines can even play a protective role by either counteracting the development and function of Th1 cells or dampening the activity of Th1-activated macrophages [4,6]. Thus, it is reasonable that Th2 cells are less susceptible than Th1 cells to the suppressive activity of natural Treg cells. In addition, the observation
that Th2 cells are poorly susceptible to, and can easily escape from, the activity of CD25+ Treg could contribute to explain the chronicization of inflammation observed in several allergic Th2-mediated disorders.
Take-home messages ! Natural regulatory cells develop in the thymus and result in an endogeneous long-lived population of T cells specific for self-antigens. ! Natural Treg cells are positively selected through a high-affinity recognition of self-peptides presented by thymic stromal cells. This likely results in signals rendering these cells anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. ! Human single-positive CD4+/ CD8+CD25+ Treg cells in fetal or post-natal thymus are more homogeneous cell subsets than that of circulating Treg cells. ! Treg thymocytes constitutively express mRNA for Foxp3 and GITR as well as CD25, TNF-aRII, CCR8, CTLA-4 and TGF-h1 on their surface, which are common features of mature Treg cells. ! Treg cells act trough a cell-to-cell contact mechanism involving mCTLA-4 and mTGF-h1 interactions with their own ligands/receptors and leading to the downregulation of the expression of IL-2R a chain on target T cells. ! Treg cells exert higher suppressive activity on Th1 than on Th2 cells.
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lymphocytes by stimulation in the presence of TGF-{beta}. J Immunol 2005;174:1446 – 55. [39] Chen W, Jin W, Wahl SM. Engagement of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) induces transforming growth factor h (TGF-h) production by murine CD4+ T cells. J Exp Med 1998;188:1849 – 57. [40] Campbell JDM, Cook G, Robertson SE, Fraser A, Boyd KS, Alastair Gracie J, et al. Suppression of IL-2-induced T cell proliferation and phosphorylation of STAT3 and STAT5 by tumor-derived TGF-h is reversed by IL-15. J Immunol 2001;167:553 – 61. [41] Cosmi L, Liotta F, Angeli R, Mazzinghi B, Santarlasci V, Manetti R, et al. Th2 cells are less susceptible than Th1 cells
to the suppressive activity of CD25+ regulatory thymocytes because of their responsiveness to different cytokines. Blood 2004;103:3117 – 21. [42] Bopp T, Palmetshofer A, Serfling E, Heib V, Schmitt S, Richter C, et al. NFATc2 and NFATc3 transcription factors play a crucial role in suppression of CD4+ T lymphocytes by CD4+CD25+ regulatory T cells. J Exp Med 2005;201: 181 – 7. [43] Suto A, Nakajima H, Kagami S-I, Suzuki K, Saito Y, Iwamoto I. Role of CD4+CD25+ regulatory T cells in T helper 2 cellmediated allergic inflammation in the airways. Am J Respir Crit Care Med 2001;164:680 – 7.
Screening of an endothelail cDNA library identifies the C-terminal region of Nedd5 as a novel autoantigen in SLE with psychiatric manifestations. Anti-endothelial-cell antibodies are associated with psychiatric manifestations in systemic lupus erythematosus (SLE). In this study Margutti P. et. al. (Arthritis Res Ther 2005;7: R896-903) aimed to seek and characterize molecules that behave as endothelial autoantigens in SLE patients with psychiatric manifestations. By screening a cDNA library from human umbilical artery endothelial cells with serum from an SLE patient with psychosis, the authors identified one positive strongly reactive clone encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. To evaluate anti-Nsdd5 serum immunoreactivity, they analyzed by ELISA for specific IgG responses in 17 patients with SLE and psychiatric manifestations (group A), 34 patients with SLE without psychiatric manifestations (group B), 20 patients with systemic sclerosis, 20 patients with infectious mononucleosis, and 35 healthy subjects. IgG specific to Nedd5 C-ter was present in 14 (27%) of the 51 SLE patients. The mean optical density value for IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients of group A than in those of group B, those with infectious mononucleosis, or healthy controls (0.17+/- 0.14 vs, respectively, 0.11 +/- 0.07, p = 0.04; 0.11 +/- 0.06, p = 0.034; and 0.09 +/- 0.045, p = 0.003, on Student’s test). In conclusion Nedd5 is a novel autoantigen of potential clinical importance that could be successfully used for a more thorough investigation of the pathogenesis of psychiatric manifestations in SLE.
Treatment with chimeric anti-human CD40 antibody suppresses MRI-detectable inflammation and enlargement of pre-existing brain lesions in common marmosets affected by MOG-induced EAE. Common marmosets, a neotropical monkey species, are protected against clinical and neuropathological consequences of experimentally induced autoimmune encephalomyelitis (EAE) by prophylactic treatment with ch5D12, a humanized antagonist antibody against human CD40. Hart BA. et. al. (J Neuroimmunol 2005; 163: 31-9) have tested whether ch5D12 acts therapeutically against the enlargement and inflammatory activity of existing (brain) white matter lesions using serial magnetic resonance imaging (MRI). The results show in all PBS treated monkeys (n = 4) a rapid enlargement of T2 lesions due to inflammatory edema. Treatment with ch5D12 delayed the enlargement of T2 lesions in 2 out of 3 tested monkeys and in 3 out of 3 monkeys the T2 signal increment of lesions was suppressed. The current findings support antibody-mediated blockade of CD40 interaction with its ligand CD154 as a potential treatment of MS.
Thymic regulatory T cells Enrico Maggi*, Lorenzo Cosmi, Francesco Liotta, Paola Romagnani, Sergio Romagnani, Francesco Annunziato Center of Research, Transfer, High Education dMCIDNENT T, University of Florence, Firenze, Italy Available online 16 May 2005
Abstract Several types of T regulatory (Treg) cells have been described in both mice and humans, including natural or professional (CD4+CD25+ T cells) and adaptive (Th3 and Tr1 cells) Treg cells. The former develops in the thymus and results in an endogeneous long-lived population of self-antigen-specific T cells in the periphery poised to prevent potentially autoimmune reactions. The second subset develops as a consequence of activation of mature T cells under particular conditions of suboptimal antigen exposure and/or costimulation. Natural Treg cells are positively selected in the cortex through their TCR interactions with self-peptides presented by thymic stromal cells. It is likely that this high-affinity recognition results in signals rendering them anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. Recently, small subsets of CD4+CD25+ and of CD8+CD25+ cells sharing similar characteristics have been detected in human fetal and post-natal thymuses. Both CD4+CD25+ and CD8+CD25+ human thymocytes express Foxp3 and GITR mRNA, as well as surface CCR8 and TNFR2 and cytoplasmic CTLA-4 proteins, which are common features of mature Treg cells. Following activation they do not proliferate or produce cytokines, but express surface CTLA-4 and TGF-h1. They suppress the proliferation of autologous CD4+CD25 thymocytes to allogeneic stimulation by a contact-dependent mechanism related to the combined action of surface CTLA-4 and TGF-h leading to the inhibition of the IL-2R a chain on target T cells. Lastly, both CD4+CD25+ and CD8+CD25+ Treg thymocytes exert strong suppressive activity on Th1, but much lower on Th2 cells, since these latter may escape from suppression via their ability to respond to growth factors other than IL-2. Treg cells that develop in, and emerge from, the thymus are certainly responsible for the maintenance of selftolerance and prevention of autoimmune disorders. The result that Th1 cells are highly susceptible to the suppressive activity of Treg thymocytes is consistent with the important role of these cells in protecting against the Th1-mediated immune response to autoantigens. D 2005 Elsevier B.V. All rights reserved. Keywords: Autoimmunity; CD4+CD25 +/CD8+CD25+ T-regulatory cells; Foxp3; Immunoregulation; Thymus
* Corresponding author. Centro di Ricerca, Trasferimento e Alta Formazione dMCIDNENTT, Universita` di Firenze, Policlinico di Careggi, Viale Morgagni, 85, 50134 Firenze (I), Italy. Tel.: +39 55 4296429; fax: +39 55 4296449. E-mail address: [email protected] (E. Maggi). 1568-9972/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.autrev.2005.04.010
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1. Introduction Autoimmune disorders are characterized by a breakdown in the mechanisms of tolerance to selfantigens. The negative selection of autoreactive thymocytes is the first self-tolerance mechanism occurring in the thymus but, even if it is high efficient, a number of self-reactive cells overcome the selection barrier [1]. Thus, autoreactive T cells may be activated by peripheral tissues- or self-mimicking exogeneous antigens leading to subsequent autoaggression [2]. Even though circulating autoreactive T cells are present in all individuals, the prevalence of autoimmune disorders affects only a minimal proportions of subjects, suggesting that mechanisms of peripheral tolerance operate to silence potentially pathogenetic T cells. In the last decade there has been an intense focus on the role of Treg cell in controlling immune responses and several types of Treg cells have been identified in both mice and humans [3]. They include cross regulatory Th1 and Th2 cells, CD4+ T cells producing soluble TGF-h 1 (Th3 cells), which are able to inhibit the outcome of some autoimmune disorders [4,5] and CD4+ T regulatory 1 (Tr1) cells producing high levels of IL-10 and inhibiting some Tcell responses in vivo [6]. Also CD8+CD28 cells, natural killer T (NKT) cells, g y T cells have been included into Treg cell family [7–9]. Finally, another Treg cell subset, characterized by the constitutive high expression of the IL-2R a chain (CD25high), which is called as the CD4+CD25+ Treg population, has been demonstrated in the thymus and peripheral blood (PB) from both mice and humans [10]. Neonatally thymectomized mice, which are deficient in this population of T cells, develop multiorgan autoimmune disease, which can be overcome by the adoptive transfer of CD4+CD25+ cells from normal mice, thus suggesting a central role of these cells in self-tolerance [2]. In addition, adult thymectomy and subsequent sublethal X-irradiation produce thyroiditis and type 1 diabetes in selected strains of mice [2,3]. There is now a general consensus that the thymic Treg cells are involved in active mechanism of peripheral tolerance of autoreactive T cells that have escaped thymic selection [2–5]. Based on extensive data in mouse models, two subsets of Treg cells have been proposed which differ
in terms of specificity and effector mechanisms: the natural (namely the CD4+CD25+ Treg cells) regulatory cells, also defined bprofessional TregQ, develop in the thymus and result in an endogeneous long-lived population of self-antigen-specific T cells in the periphery poised to prevent potentially autoimmune reactions. The second subset namely badaptive regulatory cellsQ (Tr1, Th3 and other cells) develops as a consequence of activation of mature T cells under particular conditions of sub-optimal antigen exposure and/or costimulation [11]. In this article, we will analyse the recent progress of developmental and functional features of naturally regulatory CD25+ thymocytes in mouse as in man.
2. Origin and development of Treg thymocytes Thymus produces the majority of CD25+ CD4+ Treg cells as a functionally mature T-cell subpopulation, which appears to be a distinct cellular lineage similar to circulating Treg cells. Since adoptive transfer of mature thymocytes, depleted of CD25+ T cells, induced several autoimmune diseases in syngeneic T-cell-deficient mice, it has been suggested that the normal thymus is continuously producing self-reactive CD4+ effector T cells as well as selfreactive natural Treg cells able to suppress them. This activity has been defined as the third function of the thymus [12]. Natural Treg cells develop in the thymus during the early stages of fetal and neonatal T-cell development. In mouse they are polyclonal and potentially able to recognize various self-antigens. However, the cellular basis of their maturation, the role of antigen presentation, the diversity of TCR usages and interactions with thymic microenvironment are at present unclear. By using a double transgenic mouse system, it has been shown that antigen-specific Treg cells seem to develop as a consequence of high-affinity antigen recognition. It is not known why some thymocytes escape negative selection and differentiated into Treg cells [13]. It has been proposed that they recognize tissue antigens selectively expressed by dislandsT of medullary epithelial cells, leading to a localized strong Treg cell response. Several results pointed to thymic medulla as the site for selection of CD4+CD25+ T cells in mouse, even though the
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regulatory phenotype appeared only when cells have reached the single-positive state, which is late in the selection process [13]. Other studies pointed to thymic cortex as the site for positive selection of CD4+CD25+ Treg cells, prevalently based on the expression of MHC class II by thymic cortical epithelial cells [14]. Accordingly, it has been shown that Treg cells are positively selected through their TCR affinity interactions with self-peptides presented on MHC class II molecules by thymic stromal cells. Thereafter, some data indicate that these cells are negatively selected in the medulla and deleted, even though they are less sensitive than their CD25-counterparts to agonist-induced clonal deletion [15]. Thus, Treg cell selection looks like the selection processes of other thymocytes, the only difference being in the avidity of interactions. It has been suggested that a special range of avidity results in both selection of Treg cells and the delivery of some signals leading these cells anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. It has been proposed that this protective molecule may be the glucocorticoidinduced TNF receptor (GITR) which displays an anti-apoptotic activity [16]. The presence in human fetal and post-natal thymus of subsets of mature CD4+ or CD8+ thymocytes expressing high levels of CD25 and displaying the same features of circulating CD4+CD25high regulatory cells has been recently shown [17–20]. No conclusive data, however, have been achieved on whether Treg cells follow a developmental pathway as a separate lineage or whether they are generated by differences in signalling during TCR selection. It has been shown that in human fetal thymus the CD25 molecule is acquired at the 13–17 weeks of gestation, at the CD1a+ stage during the acquisition of CD27 expression by CD4+CD8+ double-positive thymocytes. Moreover, the first CD8+CD25+ cells are found in the fetus in the subsequent CD1a+CD27+ stage. Finally, in the most mature CD1a CD27+ stage only CD4+CD8+ double-positive and CD4 single-positive thymocytes express high levels of CD25, while a small proportion of CD8 single-positive cells shows lower CD25 expression [19]. The molecular signals initiating this lineage decision remain to be defined, even though they may be linked to the strength of TCR signalling and/or to repertoire of self-peptides
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presented. According to some authors, upon exit from the thymus Treg cells enter into the circulation as naı¨ve CD45RA+GITR T cells, indeed they are able to suppress proliferation of polyclonally activated effector cells but still lack the capacity to react, or suppress responses, against autoantigens [19]. This occurs upon the transition within the fetal secondary lymphoid organs, where they acquire a more memorylike phenotype. However, it cannot be excluded that some conventional CD4+CD25 Treg cells are converted to CD4+CD25+ Treg in the periphery [21]. As a result, activated Treg cells express CD69, GITR and CD45RO and are able to suppress a broad range of response, namely due to autoreactive T effector cells escaping from thymic selections.
3. Phenotypic profile of Treg thymocytes Mouse natural Treg cells constitutively express a variety of cell surface molecules such as CD25high, CD45ROlow, CD62L, CD103, GITR and CTLA-4. Neutralising anti-GITR antibody is able to block Treg suppression in vitro and to induce autoimmune disorders in vivo by increasing proliferation of Treg cells through transduction of a costimulatory signal, and rendering effector T cells resistant to suppressive activity of Treg cells [22]. Also Neutropilin-1, a semaphoring III receptor molecule initially described to be an essential component of the immunological synapse, is highly expressed on natural Treg cells and downregulated upon their activation [23]. A deeper understanding of the developmental processes of natural Treg cells has been achieved also with the Foxp3 gene. It has been recently shown that such gene, encoding a forkhead/winged-helix family transcriptional repressor, is predominantly expressed in Treg cells in the thymus and periphery in mouse as in man [24]. The transfection of naı¨ve T cells with Foxp3 mRNA makes them anergic and suppressive resembling the phenotype and functional features of Treg cells. Adoptive transfer of these cells is able to prevent autoimmune disorders in vivo. Foxp3/FOXP3 may be considered a master regulatory gene for celllineage commitment and developmental differentiation for Treg cells from thymus and periphery. This gene is mutated in the mouse strain scurfy and in
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humans suffering from immune dysregulation polyendocrinopathy enteropathathy, X-linked syndrome (IPEX) [24]. Phenotypic profile of human Treg cells in the thymus is very similar to that described in mouse. CD4+CD25+ human Treg cells in post-natal thymus constitutively express Foxp3 and GITR mRNA [20], as well as surface TNF receptor 2 (TNFR2), and cytoplasmic CTLA-4 proteins [18]. More importantly, virtually all cells express on their surface CTLA-4 and the majority of them also membrane TGF (mTGF)-h 1 if stimulated with anti-CD3 plus anti-CD28 mAbs [18]. mRNA expression as well as surface analysis has revealed that the chemokine receptor CCR8 is constitutively expressed by CD4+CD25+ thymocytes, indeed the CCR8-ligand, I-309/CCL1 selectively attract these cells [18]. Interestingly, it was found that the CD4+CD25+ thymocytes primarily localize in the medulla, mainly in perivascular areas of the fibrous septa where epithelial cells and macrophages produce I-309/CCL1. It may be suggested that CCR8–CCL1 interaction can be involved in the spread of mature CD4+CD25+ into circulation [18]. A further subset of human regulatory thymocytes being CD8+CD25+ cells has been recently described [20]. The CD8+CD25+ thymocytes share similar phenotypic characteristics with CD4+CD25+ thymocytes, since they may be detected in the same areas of human thymus and, more importantly, they constitutively express Foxp3 and GITR mRNA. CD8+CD25+ thymocytes express both surface and cytoplasmic markers of CD4+CD25+ thymocytes whereas, differently from CD8+CD25+ effector T cells, they did not exhibit the presence of either perforin or granzyme A. Following polyclonal stimulation, CD8+CD25+ thymocytes do not produce any cytokine, but express both CTLA-4 and TGF-h 1 on their surface [20]. The physiological meaning of CD8+CD25+ Treg thymocytes is presently unclear. As previously reported, it has been suggested that CD4+CD25+ thymocytes might be educated during the selection steps to recognize self-antigens that are presented on MHC class II molecules by stromal cells in a process that is known as baltered negative selectionQ, after which they migrate directly to peripheral lymphoid tissues [13–15]. Similar explanation might be provided for CD8+CD25+ thymocytes with the only difference that these cells are educated to recognize self-antigens
that are presented on MHC class I molecules by cells present in the thymic microenvironment. After their migration to the peripheral lymphoid tissue, CD8+CD25+ Treg cells may be involved in the regulation of T-cell responses directed against viruses and transformed cells, which are usually exploited by cytotoxic CD8+ T lymphocytes. Lastly, the enrichment of CD25+ thymocytes by sorting procedure results in the clear isolation of different thymocyte subsets. In particular, based on the CD4 and CD8 expression, we were able to identify another CD25+ T-cell population (namely CD4+CD8+CD25+) which showed some features of regulatory cells. They constitutively expressed Foxp3 mRNA and were also able to suppress the proliferation of autologous CD4+CD25 thymocytes. However, it is not clear if this new subset can be related to the model described above in the mouse (Liotta F. et al., manuscript in preparation). In the fetal thymus CD4+CD25+ T cells display surface features similar to that reported of post-natal thymocytes: expression of GITR, CD122 and intracellular CTLA-4, in contrast with low expression of CD127. Also CD8+CD25+ thymocytes developed in the fetal thymus share many of characteristics with their CD4+ counterparts, as well as with the CD8+CD25+ Treg cells found in post-natal thymus. Of note, CD25+ fetal thymocytes have the potential to suppress proliferative response of autologous CD25 T cells as mature natural Treg cells [19].
4. Functional features of Treg thymocytes and mechanisms of suppression The main feature of CD25+ Treg cell subsets is their ability to downregulate immune responses. They are able to inhibit several cells involved in both innate and adaptive immune mechanisms. CD4+CD25+ Treg cells require TCR triggering, and probably IL2, to exert their suppressive effects, which are not specific towards bystander cells [25]. In mice Treg cells are anergic in vitro and do not produce IL-2 in response to conventional stimuli. However, this anergy can be overcome by high doses of IL-2, or anti-CD28 costimulus, or the use of mature DC. In vivo Treg cell anergy is rarely found and they appear to have a high turnover [26].
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Similarly to mouse Treg cells, human CD4+CD25+ and CD8+CD25+ regulatory thymocytes from both fetal and post-natal thymus show poor, if any, proliferation in response to mitogenic and mixed lymphocyte culture (MLC) stimulation and suppressed in a dose-dependent fashion the proliferative response to allogeneic stimulation of autologous CD4+CD25 thymocytes. These cells do not produce IL-2, IL-4, IL-5, IL-13, IFN-g , and only a few of them produced IL-10, upon polyclonal stimulation [18,20]. Even though the immunoregulation is the main feature of Treg cells, the fine mechanisms of suppression remain elusive. There is a general consensus that they act through a cell-to-cell contact mechanism without any effect by soluble factors produced by them or by target T cells [18,20,27]. The cell-to-cell contact mechanism involved in the suppressive activity of Treg cells has yet to be clarified. Recently, it has been shown that Treg cells may act as an IL-2 sink, depriving autoreactive T cells of autocrine IL-2 [28]. Other mechanisms include CTLA-4, an inhibitory molecule highly expressed by Treg cells. CTLA-4 has been recently shown to trigger the induction of indoleamine 2,3-dioxygenase (IDO) by DC, which catalyzes the tryptophan conversion into kinurenins, molecules showing immunosuppressive effects on several cells [29]. Some authors have also shown that Treg cells are able to downregulate the expression of costimuli (namely CD80, CD86) on DC, thus modifying their APC capacity. It has also been suggested that the engagement of CD80 and, to a lesser extent, of CD86 on the responder T cells was responsible for the negative signal given by Treg cells [30]. In human Treg thymocytes we found that the suppressive activity was partially but consistently inhibited by neutralizing antibodies towards CTLA4, TGF-h1, or TGF-h1R [18,20]. More importantly, such a suppressive activity was completely abolished by a mix of anti-CTLA-4 and anti-TGF-h1 mAbs, thus indicating that these molecules are both involved in the suppressive activity. This finding is not fully consistent with those studies performed so far by using PB CD4+CD25+ T cells, which failed to demonstrate any impairment of suppression with antiCTLA-4 or anti-TGF-h Abs [17,31,32]. This discrepancy may be due to either the heterogeneity of PB in comparison with thymus-derived CD4+CD25+ T
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cells, or to the different assays used to assess the suppressive activity. However, it has been recently shown that the suppressive activity of CD4+CD25+ murine T cells was abolished by the neutralization of TGF-h1 and that activated CD4+CD25+ T cells expressed high and persistent levels of membrane TGFh1 [33–35]. Of note, recent studies on human cells clearly showed the crucial role of TGF-h1 in the induction of the regulatory phenotype in CD4+ CD25 cells [36–38]. As previously reported, the role of CTLA-4 in the regulatory activity of murine CD4+CD25+ T cells has been clearly demonstrated in vivo. Since CTLA-4 engagement has been found to enhance the secretion of TGF-h [39], it is reasonable to explain why in our study a complete inhibition of the suppressive activity exerted by activated human Treg thymocytes could be achieved only with the contemporaneous neutralization of both CTLA-4 and TGF-h1. The results obtained by using the highly homogeneous human CD8+ or CD4+CD25+ Treg thymocyte populations provided new insights in the understanding the mechanisms by which Treg cells suppress the proliferative response of stimulated CD4+CD25 cells. CD4+CD25 cells in the presence of CD25+ regulatory thymocytes were unable to express the IL2R a chain and, therefore, became unresponsive to IL2. Moreover, the inability of effector T cells to proliferate was not affected by the addition of exogenous IL-2, but it was overcome by the addition of IL-15, a T-cell stimulatory cytokine that does not share the high-affinity IL-2R a chain [18]. These findings are consistent with a study, showing that suppression of IL-2-induced human T-cell proliferation and phosphorylation of STAT3 and STAT5 by TGF-h1 may be completely overcome by treating T cells with IL-15 [40]. More recently, we asked whether human Treg thymocytes exerted different suppressive activity on Th1 or Th2 polarized effectors. T-cell clones were generated from CD25+ thymocytes, (both CD4+ and CD8+) and their suppressive activity was evaluated on Th1 or Th2 T-cell clones derived from autologous CD4+CD25 thymocytes [41]. The results indicate that the proliferation of Th1 clones was completely suppressed by both CD4+ and CD8+ autologous Treg cells, whereas the same Treg cells exhibited much lower suppressive activity on Th2 clones. This
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difference was due to the ability of Th2 cells to produce cytokines that allow them to proliferate even in the absence of responsiveness to IL-2. Indeed, the suppressive activity of CD25+ thymocytes on Th2 clones was enhanced by neutralization in culture of IL-4, whereas it was completely blocked by the addition of recombinant IL-4, IL-7, IL-9, and IL-15. By contrast, the proliferation of Th1 cells was only restored by the administration in culture of IL-15. Accordingly, Th2 clones expressed significantly higher levels of IL-4R and IL-9R mRNA than Th1 clones, whereas the expression on Th1 and Th2 cells of IL-2R, IL-7R, and IL-15R was comparable [41]. These data suggest that, although Treg cells regulate both Th1 and Th2 responses downregulating the expression of IL-2R in effector T cells, Th2 cells may partially escape to this suppressive activity via their ability to respond to grow factors different from IL-2 such as IL-4, IL-7 and IL-9. In particular IL-4, produced by Th2 cells and acting in an autocrine fashion, can, at least in part, bypass the regulatory effects exerted by CD4+CD25+ Treg cells. Accordingly, CD4+CD25 cells from NFATc2 / c3 / double knockout mice, which develop massive lymphadenopathy, splenomegaly and strong increase in serum IgE and IgG1 levels, caused by preferential differentiation of naive T cells into Th2 cells, are unresponsive to CD4+CD25+ Treg suppression, even in the absence of exogeneous IL-4 [42]. Finally, these data are consistent with the observation that depletion in mice of CD4+CD25+ T cells prevents antigen-induced Th2 differentiation by increasing the differentiation of Th1 cells [43]. The demonstration that both CD4+CD25+ and CD8+CD25+ Treg thymocytes can exert strong suppressive activity on Th1, but much lower on Th2, cells is of great potential interest. In fact, while autoimmune diseases are mainly associated with Th1-mediated immune responses [2,4,6], the Th2 cells are more rarely detectable in tissues affected by autoimmune disorders and their cytokines can even play a protective role by either counteracting the development and function of Th1 cells or dampening the activity of Th1-activated macrophages [4,6]. Thus, it is reasonable that Th2 cells are less susceptible than Th1 cells to the suppressive activity of natural Treg cells. In addition, the observation
that Th2 cells are poorly susceptible to, and can easily escape from, the activity of CD25+ Treg could contribute to explain the chronicization of inflammation observed in several allergic Th2-mediated disorders.
Take-home messages ! Natural regulatory cells develop in the thymus and result in an endogeneous long-lived population of T cells specific for self-antigens. ! Natural Treg cells are positively selected through a high-affinity recognition of self-peptides presented by thymic stromal cells. This likely results in signals rendering these cells anergic and able to produce anti-apoptoptic molecules which protect them from negative selection. ! Human single-positive CD4+/ CD8+CD25+ Treg cells in fetal or post-natal thymus are more homogeneous cell subsets than that of circulating Treg cells. ! Treg thymocytes constitutively express mRNA for Foxp3 and GITR as well as CD25, TNF-aRII, CCR8, CTLA-4 and TGF-h1 on their surface, which are common features of mature Treg cells. ! Treg cells act trough a cell-to-cell contact mechanism involving mCTLA-4 and mTGF-h1 interactions with their own ligands/receptors and leading to the downregulation of the expression of IL-2R a chain on target T cells. ! Treg cells exert higher suppressive activity on Th1 than on Th2 cells.
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Screening of an endothelail cDNA library identifies the C-terminal region of Nedd5 as a novel autoantigen in SLE with psychiatric manifestations. Anti-endothelial-cell antibodies are associated with psychiatric manifestations in systemic lupus erythematosus (SLE). In this study Margutti P. et. al. (Arthritis Res Ther 2005;7: R896-903) aimed to seek and characterize molecules that behave as endothelial autoantigens in SLE patients with psychiatric manifestations. By screening a cDNA library from human umbilical artery endothelial cells with serum from an SLE patient with psychosis, the authors identified one positive strongly reactive clone encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. To evaluate anti-Nsdd5 serum immunoreactivity, they analyzed by ELISA for specific IgG responses in 17 patients with SLE and psychiatric manifestations (group A), 34 patients with SLE without psychiatric manifestations (group B), 20 patients with systemic sclerosis, 20 patients with infectious mononucleosis, and 35 healthy subjects. IgG specific to Nedd5 C-ter was present in 14 (27%) of the 51 SLE patients. The mean optical density value for IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients of group A than in those of group B, those with infectious mononucleosis, or healthy controls (0.17+/- 0.14 vs, respectively, 0.11 +/- 0.07, p = 0.04; 0.11 +/- 0.06, p = 0.034; and 0.09 +/- 0.045, p = 0.003, on Student’s test). In conclusion Nedd5 is a novel autoantigen of potential clinical importance that could be successfully used for a more thorough investigation of the pathogenesis of psychiatric manifestations in SLE.
Treatment with chimeric anti-human CD40 antibody suppresses MRI-detectable inflammation and enlargement of pre-existing brain lesions in common marmosets affected by MOG-induced EAE. Common marmosets, a neotropical monkey species, are protected against clinical and neuropathological consequences of experimentally induced autoimmune encephalomyelitis (EAE) by prophylactic treatment with ch5D12, a humanized antagonist antibody against human CD40. Hart BA. et. al. (J Neuroimmunol 2005; 163: 31-9) have tested whether ch5D12 acts therapeutically against the enlargement and inflammatory activity of existing (brain) white matter lesions using serial magnetic resonance imaging (MRI). The results show in all PBS treated monkeys (n = 4) a rapid enlargement of T2 lesions due to inflammatory edema. Treatment with ch5D12 delayed the enlargement of T2 lesions in 2 out of 3 tested monkeys and in 3 out of 3 monkeys the T2 signal increment of lesions was suppressed. The current findings support antibody-mediated blockade of CD40 interaction with its ligand CD154 as a potential treatment of MS.