Downregulation of Innate B Cells, B-1a and MZB, by iNKT Cells

Abstracts Professor, University of Calgary, Department of Pharmacology and Therapeutics, Calgary, AB, Canada The reason why particular inhaled antigens induce allergic sensitization and prevent the development of immune tolerance is unclear. Intrinsic characteristics of these antigens must be of importance. A common characteristic of many potent allergens is that they either possess serine proteinase activity or are inhaled in particles rich in serine proteinases. Many allergens, such as house dust mite, have the potential to activate the Proteinaseactivated Receptor-2 (PAR-2). We hypothesized that PAR-2 activation by such allergens is crucial to facilitate our allergic sensitization to them. To test our hypothesis we used a Balb/c murine system with mucosal exposure to OVA, as an antigen, with a PAR-2 activating peptide (PAR2AP) to mimic the potential of a proteolytic allergen, or other inhaled proteinases, to activate PAR-2. Upon allergen re-exposure mice initially administered OVA with the PAR2AP developed airway inflammation, airway hyperresponsiveness (AHR), produced OVA-specific IgE as well as OVAspecific T cells with a Th2 cytokine profile. Conversely, mice given OVA alone or with a control peptide (PAR-2CP) developed tolerance. These immune tolerant mice did not develop airway inflammation, AHR, or OVA-specific IgE, but developed OVA-specific T cells that secreted high levels of IL-10 indicative of Treg cell function. Finally, we showed that this PAR-2-mediated allergic sensitization was TNF dependent. Thus, PAR-2 activation in the airways could be a critical factor in the development of allergic sensitization following mucosal exposure to allergens with serine proteinase activity. Interfering with this pathway may prove to be useful for the prevention or treatment of asthma. doi:10.1016/j.clim.2007.03.383

OR.66 Downregulation of Innate B Cells, B-1a and MZB, by iNKT Cells Xiangshu Wen, Postdoctoral Fellow, University of California, Los Angeles, Medicine, Los Angeles, CA, Jun-Qi Yang, Assistant Research Professor, UC, Medicine, Cincinnati, OH, Ram Raj Singh, Professor, University of California, Los Angeles, Medicine, Los Angeles, CA B cells are essential for the development of autoimmune diseases such as lupus. Although all mature B cell subsets can produce autoantibodies, several lines of evidence implicate innate B cells, namely B-1a and marginal zone B (MZB) cells, in the development of such diseases. Here, we investigated the role of interaction between innate B cells that express high levels of CD1d and CD1d-reactive iNKT cells in the regulation of autoantibodies. We found that whereas activated iNKT cells increase activation markers CD69 and CD86 on all B cell subsets, they selectively reduce the frequency of B-1a and MZB cells. In resonance with such regulatory role, the proportions of MZB cells are increased in iNKT cell deficient (Ja18−/−) mice, whereas MZB cells are reduced in iNKT cell transgenic (Va14Tg) mice.

S73 Furthermore, whereas iNKT cells increase expression of activation markers and production of normal Ig via cytokines secreted by iNKT cells in transwell cultures, they selectively suppress the production of IgG anti-DNA antibody and rheumatoid factor and IL-10 by B cells in a contact-dependent manner. Such regulation of B cells by iNKT cells must be important for in vivo regulation of autoantibodies and lupus disease, as the in vivo transfer of iNKT cells in B cell-reconstituted SCID mice or in Ja18−/− mice suppresses autoantibody production. Treatment with an iNKT cell ligand also delays the onset of lupus in BWF1 mice. Thus, iNKT cells suppress autoreactive B cells and can prevent systemic autoimmunity. They do so via regulating innate B cells. doi:10.1016/j.clim.2007.03.384

OR.67 CD40 Isoform Differences and Microdomain Localization Explain Preferential Survival of CD4+CD40+ T Cells in Autoimmunity Gisela M. Vaitaitis, Professional Research Assistant, University of Colorado Health Sciences Center, WebbWaring, Denver, CO, David H. Wagner, Assistant Professor, University of Colorado Health Sciences Center, WebbWaring, Denver, CO CD40 plays a critical role in autoimmunity. CD40expressing CD4 T cells (TCD40) are expanded in autoimmunity and are necessary and sufficient in transferring disease in mouse type I diabetes. CD40 on TCD40 can have costimulatory effect and induces Nf-kB and recombinase protein expression with subsequent alteration of TCR. CD40 exists as five isoforms in mice with little known-about differences in isoform expression between cell types, between autoimmune and non-autoimmune conditions and differences in outcome of CD40 isoform signaling. Here we show that the major isoform expressed in TCD40 is isoformV with isoform-I expressed at lower levels. This differs distinctly from antigen presenting cells which predominantly express isoform-I. In autoimmune NOD the ratio of TCD40 isoform-V to -I is exaggerated and overall expression is greater compared to non-autoimmune BALB/c. It was shown in lymphocyte cell lines that CD40 and TRAF2 are not associated with detergent-insoluble microdomains (rafts) until CD40 is engaged. However, untreated NOD TCD40 have the CD40 isoforms and TRAF2 associated with this fraction while BALB/c TCD40 do not. A functional outcome of CD40 signals to NOD TCD40 is increased survival through induction of survival proteins Bcl-XL and cFLIPp43. In addition, CD40 signals to NOD TCD40 alter the outcome of Fas engagement such that Fas instead of inducing apoptosis induces increased survival beyond that of CD40 alone. Therefore TCD40 from NOD may be poised for survival even when encountering death promoting conditions explaining how this population gains the upper hand in autoimmune conditions to thwart T cell homeostasis. doi:10.1016/j.clim.2007.03.385