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Murine Trypanosoma cruzi infection: a role for TH2 cells in the immunopathology of chronic infection
IMMUNE RESPONSE IN CHAGAS" DISEASE
141
Murine Trypanosoma cruzi infection: a role for TH2 cells in the immunopathology of chronic infection M. H o n t e b e y r i e - J o s k o w i c z Unitd d'Immunoparasitologie, Institut Pasteur, 75724 Paris Cedex 15
Murine infection with Trypanosoma cruzi closely mimics Chagas' disease in humans, including the acute phase with parasitaemia and general symptoms, and the chronic phase with heart damage and tissue destruction in the absence of visible parasites (Andrade, 1983). To date, all niouse strains studied develop parasitaemia followed by tissue destruction. No spontaneous cure of the infection has been described in either man or mouse. Although protective and pathologic mechanisms are not yet fully understood, the role of the specific humoral antibody response in controlling the parasitaemia has been well documented (Krettli and Brener, 1976; Martins et al., 1985; Plata et a!~ ! 987). The presence of high levels of autoantibodies in sera from infected humans or mice does not appear to be responsible for pathological effects but seems rather to be the consequence of extensive polyclonal B-cell activation (Minoprio et al., 1986). A direct effect of the autoantibodies on chronic chagasic pathology remains to be demonstrated. Passive transfer of mouse chronic sera into the sciatic nerves of naive recipients fails to induce any pathology such as demyelination or the presence of mononuclear infiltrates (Sai'd et al., 1985). However, antibodies against hearthost components can participate in indirect cytotoxicity as shown recently by Laguens et ai. (1988). As regards cell-mediated immunity, experimental observations strongly suggest that T cells con-
trol, at least partly, the parasitaemia and resistance of mice to acute infection (Trischman, 1983; Gonzalvez da Costa et ai., 1984). Neonatally thymectomized or n u / n u mice present higher parasitaemia and less resistance to acute infection than normal mice (Schmunis et al., 1971 ; Kierszenbaum and Pienkowski, 1979; Minoprio et al., 1987). In vivo treatments with monoclonal antibodies (mAb) against T cell surface markers indicate that both CD4 ÷ and CD8 + T cells may play a role in determining resistance in the acute phase of infection by controlling parasitaemia and antibody production (Minoprio et al., 1987; Russo et al., 1988; Tarleton et al., 1990). In the chronic stage, parasite-specific TH cell activity has been described (Burgess et ai., 1981), and protection against acute infection has been obtained after passive transfer of T. cruzi-specific T-cell clones (Nickell et al., 1987). Since the T-cell clones in this experiment were derived from T. cruzihyperimmune mice challenged twice with living parasites during the chronic stage of infection, it is possible that parasite challenge is important in the selection of protective clones (Nickell et ai., 1987). This suggests that repeated infections in humans might have a beneficial effect on the establishment of protective immunity in endemic areas. The observation that nonadherent spleen cells and later that CD4+-enriched T lymphocytes were able to reproduce the tissue pathology of the chronic stage of
infection by passive transfer into naive recipients, strongly suggests that CD4 + T cells may have a role in promoting disease (Laguens et al., 1981 ; Sai'd et al., 1985). Consequently, we have focussed most of our attention recently on the study of T cells involved in the immunopathology of mice chronically infected with T. cruzi. T cells mediating pathology are present in the circulation of chronically infected mice, and are able to transfer a local delayed-type hypersensitivity reaction (DTH) in the presence of total parasite extract (Hontebeyrie-Joskowicz et al., 1987). This observation is controversial when compared with the data of Scott (1981) showing suppresa,u,, u1 ,.,u,~-ar, ct:,t~: DTH nl chronic infection. Possible explanations are" (1) a decrease of circulating monocytes that could be recruited by T cells for the establishment of the DTH reaction in infected animals (Plata et ai., 1986), or (2) a different pattern of T-cell activity occurring in spleen and lymph nodes from infected mice (Curotto de Lafaille et al., 1990; L6wy et al., 1982). However, T. cruzi-specific DTH has been shown to be involved in the induction of the numerous cellular infiltrates observed in mice chronically infected with T. cruzi (Hontebeyrie-Joskowicz et al., 1987). T. cruzi-specific CD4+ T-cell lines have been developed in vitro and have been shown to be able to transfer in vivo a local DTH reaction when injected into the foot-
142 pads of naive recipients in the presence of T. cruzi extracts. Systemic or intraneural injections of these T-cell lines induce inflammatory infiltrates similar to those of infected mice, as shown by the massive recruitment of mononuclear cells (Ben YounesChennoufi et al., 1988a). Because these T. cruzi-specific T-cell lines were stimulated in vivo with total parasite extracts i.e. whole trypomastigotes frozen and thawed 3 times, we cannot determine the epitopes involved in the parasite-specific response. Further studies will be necessary to define the parasite polypeptides responsible for stimulation of the T cells mediating pathology in vivo. The experimental evidence strongly suggests that cross-reactive epitopes may play a role in the stimulation of Tmn cells. A significant degree of functional cross-reactivity is shared between parasite antigens and mouse peripheral nerves (HontebeyrieJoskowicz et al., 1987). The recent findings of parasite recombinant polypeptides carrying crossreactivities (Van Voorhis and Eisen, 1989) or sequence homologies (Mesri et al., 1990) with host proteins opens the way to the identification of me l -ceil epltopes involved in the pathology of T. cruzi infection. The presence of parasite antigens -- cross-reactive or not -at the surface of muscle cells of chronically infected mice (Ben Younes-Chennoufi et al., 1988b) associated with the expression of MHC class II (Ia) molecules (Laguens et al., this Forum) on the same cells strongly argues in favour of unusual antigen presentation by muscle cells. In order to further characterize the T-cell lines mediating pathology, we studied the helper function and lymphokine secretion of one of the isolated T. cruzi-specific T-cell lines (Spinella et al., 1990). This line, named G-05, derived from lymph nodes of chronically infected mice, has the feature of a TH2-cell line in inducing B cells to
36th F O R U M I N I M M U N O L O G Y
secrete Ig and secreting IL4 but not IL2 or yIFN. The B cell helper activity may be mediated by lymphokines secreted into the culture medium, namely IL4, IL5 and IL6 that share potentially B-cell stimulating activity. This T-cell line or its supernatant induces in vivo B-cell activation similar to that observed in infected animals, including a distinct pattern of isotypes (mainly IgG2a and IgG2b). Such B-cell activation may be considered to be polyclonal, independent of the presence of parasite antigens for its expression in vivo. Indeed, parasite antigens are needed to prime TH2 T cells in vivo and to stimulate them in vitro but are not necessary for the induction of B-cell activation and differentiation in vivo. Taken together, the above experimental data show that TH2 cells may mimic several features of the immunopathology in mice chronically infected with T. cruzi including (1) mediation of a DTH reaction leading to tissue mononuclear infiltrates; and (2) mediation of B cell helper function -- leading to polyclonal activation with an isotypic pattern similar to that of chronic infection with a majority of IgG2 isotypes (l~'Imnerln I.ima pt al__ IQR¢~_ ;.
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.
.
r
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
i
.
.
.
expansion of CD5 + B cells during the acute stage of infection may have a negative effect on the triggering of THI cells, allowing TH2 ceils to develop (Minoprio, this Forum). In a vaccination perspective, it is of overwhelming importance to understand the mechanisms by which the parasite commits the immune system to massive polyclonal activation. This may be done directly by a specific parasite molecule or indirectly by a factor from infected cells, such as a cytokine from mononuclear cells infected by amastigotes. The failure to sustain a permanent polyclonal activation and the lack of an inflammatory pathology with killed parasites, favours the second hypothesis. The challenge posed by Chagas' disease is to identify the molecules and cells responsible for the immunopathology. We have to define molecules (from the parasite or cytokines) and cells (from the host immune system) which trigger early polyclonal activation. In this context, it will be important to demonstrate clearly the relationship between this polyclonal activation and the later chronic pathology.
.
w e have no clear explanation for the unusual characteristics of this 7". cruzi-specific TH2 line which has the lymphokine secretion profile of a TH2 subset but the ability to mediate DTH usually found in the TH 1 subset (Cher and Mossman, 1987; Mossman et aL, 1987). The possibility of subsets existing within TH1 or TH2 cannot be excluded (Wong et al., 1988).
Recently, Fiorentino et al. (1989) have described a lymphokine (IL-10) secreted by TH2 cells that inhibits the proliferation of THI cells. It will be interesting to investigate the secretion of IL-10 by the T. cruzi-specific TH2 cell line and to look for the presence or absence of THI in vivo during all stages of infection. The
References Andrade, Z.A. (1983), Mechanismsof myocardial damage in Trypanos6ma cruzi infection, in "Cytopathology of parasitic disease" (Ciba Foundation symposium 99) (pp. 214-233). Pitman Books, London. Ben Younes-Chennoufi,A., Said, G., Eisen, H., Durand, A. & Hontebeyrie-Joskowicz, M. (1988a), Cellular immunity to Trypanosoma cruzi is mediated by helper T cells (CD4+). Trans. roy. Soc. trop. Med. Hyg., 82, 84-89. Ben Younes-Chennoufi, A., Hontebeyrie-Joskowicz, M., Tricottet, V., Eisen, H., Reynes, M. & Said, G. (1988b), Persistence of Trypanosoma cruzi antigens in the inflammatory lesions of
IMMUNE RESPONSE IN CHAGAS" DISEASE chronically infected mice. Trans. roy. Soc. trop. Med. Hyg., 82, 77-83. Burgess, D.E., Kuhn, R.E. & Carlson, K.S. (1981), Induction of parasite-specific helper T lymphocytes during Trypanosoma cruzi infections in mice. J. Immunol., 127, 2092-2095. Cher, D.J. & Mossman, T.R. (1987), Two types of murine helper T cell clone-II. Delayed-type hypersensitivity is mediated by THI clones. J. lmmunol., 138, 3688-3692. Curotto de Lafaille, M.A., Barbosa de Oliveira, L.C., Lima, G.C. & Abrahamson, I.A. (1990), Trypanosoma cruzi: Maintenance of parasite-specific T-cell responses in lymph nodes during the acute phase of infection. Exp. Parasit., 70, 161-174. D'Imperio Lima, M.R., Eisen, H., Minoprio, P., Joskowicz, M. & Coutinho, A. (1986), Persistence of polyclonal B-cell activation with undetectable parasitemia in late stages of experimental Chagas' disease. J. lmmunoL, 137, 353-356. Fiorentino, D., Bond, M. & Mossman, T. (1989), Two types of helper T cells, m IV. Th2 clones secrete a factor that inhibits cytokine production by Thl clones. J. exp. Med., 170, 2081-2092. Gonzalves da Costa, S.C., Lagrange, P.H., Hurtrel, B., Kerr, I. & Alencar, A. (1984), Role of T lvmnhr~r.wtpc in th,~ r ~ ; c t ~ . , - ~ ~ " d
immunopathology of experimental Chagas' disease. Ann. Immunol. (Inst. Pasteur), 135 C, 317-332. Hontebeyrie-Joskowicz, M., Said, G., Milon, G., Marchal, G. & Eisen, H. (1987), L3T4 + T cells able to mediate parasite-specific delayedtype hypersensitivity play a role in the pathology of experimental Chagas' disease. Europ. J. Immunol., 17, 1027-1033. Kierszenbaum, F. & Pienkowski, M. (1979), Thymus-dependent control of host defense mechanisms against Trypanosoma cruzi. Infect. Immun., 24, 117-121. Krettli, A.U. & Brener, Z. (1976), Protective effects of specific antibodies in Trypanosoma cruzi infections. J. lmmunol., 116, 755-760. Laguens, R.P., Cabeza Meckert, P., Chambo, G. & Gelpi, R.J. (1981), Chronic Chagas' disease in the mouse. -- II. Transfer of the heart disease by means of im-
munocompetent cells. Medicina (Buenos Aires), 41, 40-43. Laguens, R.P., Cabeza Meckert, P. & Chambo, J.G. (1988), Antiheart antibody-dependent cytotoxicity in the sera of mice chronically infected with Trypanosoma cruzi. Infect. Immun., 56, 993-997. Lowy, I., Joskowicz, M. & Theze, J. (1982), Characterization of suppressor cells regulating in vitro expression of lgG2a and IgG2b antibody responses. J. Immunol., 128, 768-773. Martins, M.S., Hudson, L., Krettli, A.U., Cancado, J.R. & Brener, Z. (1985), Human and mouse sera recognize the same polypeptide associated with immunological resistance to Trypanosoma cruzi infection. Clin. exp. Immunol., 61,343-350. Mesri, E.A., Levitus, G., HontebeyrieJoskowicz, M., Dighiero, G., Van Regenmortel, M.H.V. & Levin, M.J. (1990), Major Trypanosoma cruzi antigenic determinant in Chagas' heart disease shares homology with the systemic lupus erythematous ribosomal P protein epitope. J. clin. Microbiol., 28, 1219-1224. Minoprio, P., Eisen, H., Forni, L., D'lmperio Lima, M.R., Joskowicz, M. & Coutinho, A. (1986), Polyclonal lymphocyte responses to murine T. cruzi infection. I. Quantitation of both T and B responses. Scand. J. Immu•ol., 24, 661-668. ...... ,-,v,,,-,, P., t~,~¢,, ra., Joskowicz, M., Pereira, P. & Coutinho, A. (1987), Suppression of polyclonal antibody production in Trypanosoma cruzi-infected mice by treatment with anti-L3T4 antibodies. J. lmmunol., 139, 545-550. Mossman, T.R., Cherwinski, H., Bond, M.W., Giedlin, M.A. & Coffman, R.L. (1986), Two types of murine helper T cell clone. -I. Definition according to profiles of lymphokine activities and secreted proteins. J. Immunol., 136, 2348-2355. Nickell, S.P., Gebremichael, A., Hoff, R. & Boyer, M.H. (1987), Isolation and functional characterization of murine T-cell lines and clones specific for the protozoan parasite Trypanosoma cruzi. J. lmmunol., 138, 914-921. Plata, F., Milon, G., Garcia-Pons, F. & Marchal, G. (1986), Selective suppression of tumour-immune cytolytic T lymphocytes in mice with chronic Trypanosoma cruzi
143
infections. Ann. Immuno!o (Inst. Pasteur), 137 D, 47-61. Plata, F., Garcia-Pons, F. & Wietzerbin, J. (1987), Immune resistance to Trypanosoma cruzi: synergy of specific antibodies and recombinant interferon gamma in vivo. Ann. Immunol. (Inst. Pasteur), 138, 397-415. Russo, M., Starobinas, N., Minoprio, P., Coutinho, A. & HontebeyrieJoskowicz, M. (1988), Parasitic load increases and myocardial inflammation decreases in Trypanosoma cruzi-infected mice after inactivation of helper T cells. Ann. Immunol. (Inst. Pasteur), 139, 225-236. Said, G., Joskowicz, M., Barreira, A.A. & Eisen, H. (1985), Neuropathy associated with experimental Chagas' disease. Ann. NeuroL, 18, 676-683. Schmunis, G.A., Gonzalez-Cappa, S.M., Traversa, O.C. & Yanovsky, J.F. (1971), The effect of immunodepression due to neonatal thymectomy on infection with Trypanosoma cruzi. Trans. roy. Soc. trop. Med. Hyg., 65, 89-94. Scott, M.T. (1981), The nature of immunity against Trypanosoma cruzi in mice recovered from acute infection. Parasite lmmunoL, 3, 209-218. Spinella, S., Milon, G. & HontebeyrieJoskowicz, M. (1990), A CD4 + TH2 cell line isolated from mice chronically infected with Trypanosomu cruzi induces igG2 polyclonal response in vivo. Europ. J. lmmunoL, 20, 1045-1051. Tarleton, R.L. (1990), Depletion of CD8 ÷ T cells increase susceptibility and reverses vaccineinduced immunity in mice infected with Trypanosoma cruzi. J. lmmunol., 144, 717-724. Trischman, T.M. (1983), Nonantibody-mediated control of parasitemia in acute experimental Chagas' disease. J. lmmunol., 130, 1953-1957. Van Voorhis, W.C. & Eisen, H. (1989), FL- 160. A surface antigen of Trypanosoma cruzi that mimics mammalian nervous tissue. J. exp. Med., 169, 641-652. Wong, R.L., Ruddle, N.H., Padula, S.J., Lingenheld, E.G., Bergman, C.M., Rugen, R.V., Epstein, D.I. & Clark, R.B. (1988), Subtypes of helper cells. Noninflammatory type 1 helper T cells. J. Immunol., 141, 33293334.
141
Murine Trypanosoma cruzi infection: a role for TH2 cells in the immunopathology of chronic infection M. H o n t e b e y r i e - J o s k o w i c z Unitd d'Immunoparasitologie, Institut Pasteur, 75724 Paris Cedex 15
Murine infection with Trypanosoma cruzi closely mimics Chagas' disease in humans, including the acute phase with parasitaemia and general symptoms, and the chronic phase with heart damage and tissue destruction in the absence of visible parasites (Andrade, 1983). To date, all niouse strains studied develop parasitaemia followed by tissue destruction. No spontaneous cure of the infection has been described in either man or mouse. Although protective and pathologic mechanisms are not yet fully understood, the role of the specific humoral antibody response in controlling the parasitaemia has been well documented (Krettli and Brener, 1976; Martins et al., 1985; Plata et a!~ ! 987). The presence of high levels of autoantibodies in sera from infected humans or mice does not appear to be responsible for pathological effects but seems rather to be the consequence of extensive polyclonal B-cell activation (Minoprio et al., 1986). A direct effect of the autoantibodies on chronic chagasic pathology remains to be demonstrated. Passive transfer of mouse chronic sera into the sciatic nerves of naive recipients fails to induce any pathology such as demyelination or the presence of mononuclear infiltrates (Sai'd et al., 1985). However, antibodies against hearthost components can participate in indirect cytotoxicity as shown recently by Laguens et ai. (1988). As regards cell-mediated immunity, experimental observations strongly suggest that T cells con-
trol, at least partly, the parasitaemia and resistance of mice to acute infection (Trischman, 1983; Gonzalvez da Costa et ai., 1984). Neonatally thymectomized or n u / n u mice present higher parasitaemia and less resistance to acute infection than normal mice (Schmunis et al., 1971 ; Kierszenbaum and Pienkowski, 1979; Minoprio et al., 1987). In vivo treatments with monoclonal antibodies (mAb) against T cell surface markers indicate that both CD4 ÷ and CD8 + T cells may play a role in determining resistance in the acute phase of infection by controlling parasitaemia and antibody production (Minoprio et al., 1987; Russo et al., 1988; Tarleton et al., 1990). In the chronic stage, parasite-specific TH cell activity has been described (Burgess et ai., 1981), and protection against acute infection has been obtained after passive transfer of T. cruzi-specific T-cell clones (Nickell et al., 1987). Since the T-cell clones in this experiment were derived from T. cruzihyperimmune mice challenged twice with living parasites during the chronic stage of infection, it is possible that parasite challenge is important in the selection of protective clones (Nickell et ai., 1987). This suggests that repeated infections in humans might have a beneficial effect on the establishment of protective immunity in endemic areas. The observation that nonadherent spleen cells and later that CD4+-enriched T lymphocytes were able to reproduce the tissue pathology of the chronic stage of
infection by passive transfer into naive recipients, strongly suggests that CD4 + T cells may have a role in promoting disease (Laguens et al., 1981 ; Sai'd et al., 1985). Consequently, we have focussed most of our attention recently on the study of T cells involved in the immunopathology of mice chronically infected with T. cruzi. T cells mediating pathology are present in the circulation of chronically infected mice, and are able to transfer a local delayed-type hypersensitivity reaction (DTH) in the presence of total parasite extract (Hontebeyrie-Joskowicz et al., 1987). This observation is controversial when compared with the data of Scott (1981) showing suppresa,u,, u1 ,.,u,~-ar, ct:,t~: DTH nl chronic infection. Possible explanations are" (1) a decrease of circulating monocytes that could be recruited by T cells for the establishment of the DTH reaction in infected animals (Plata et ai., 1986), or (2) a different pattern of T-cell activity occurring in spleen and lymph nodes from infected mice (Curotto de Lafaille et al., 1990; L6wy et al., 1982). However, T. cruzi-specific DTH has been shown to be involved in the induction of the numerous cellular infiltrates observed in mice chronically infected with T. cruzi (Hontebeyrie-Joskowicz et al., 1987). T. cruzi-specific CD4+ T-cell lines have been developed in vitro and have been shown to be able to transfer in vivo a local DTH reaction when injected into the foot-
142 pads of naive recipients in the presence of T. cruzi extracts. Systemic or intraneural injections of these T-cell lines induce inflammatory infiltrates similar to those of infected mice, as shown by the massive recruitment of mononuclear cells (Ben YounesChennoufi et al., 1988a). Because these T. cruzi-specific T-cell lines were stimulated in vivo with total parasite extracts i.e. whole trypomastigotes frozen and thawed 3 times, we cannot determine the epitopes involved in the parasite-specific response. Further studies will be necessary to define the parasite polypeptides responsible for stimulation of the T cells mediating pathology in vivo. The experimental evidence strongly suggests that cross-reactive epitopes may play a role in the stimulation of Tmn cells. A significant degree of functional cross-reactivity is shared between parasite antigens and mouse peripheral nerves (HontebeyrieJoskowicz et al., 1987). The recent findings of parasite recombinant polypeptides carrying crossreactivities (Van Voorhis and Eisen, 1989) or sequence homologies (Mesri et al., 1990) with host proteins opens the way to the identification of me l -ceil epltopes involved in the pathology of T. cruzi infection. The presence of parasite antigens -- cross-reactive or not -at the surface of muscle cells of chronically infected mice (Ben Younes-Chennoufi et al., 1988b) associated with the expression of MHC class II (Ia) molecules (Laguens et al., this Forum) on the same cells strongly argues in favour of unusual antigen presentation by muscle cells. In order to further characterize the T-cell lines mediating pathology, we studied the helper function and lymphokine secretion of one of the isolated T. cruzi-specific T-cell lines (Spinella et al., 1990). This line, named G-05, derived from lymph nodes of chronically infected mice, has the feature of a TH2-cell line in inducing B cells to
36th F O R U M I N I M M U N O L O G Y
secrete Ig and secreting IL4 but not IL2 or yIFN. The B cell helper activity may be mediated by lymphokines secreted into the culture medium, namely IL4, IL5 and IL6 that share potentially B-cell stimulating activity. This T-cell line or its supernatant induces in vivo B-cell activation similar to that observed in infected animals, including a distinct pattern of isotypes (mainly IgG2a and IgG2b). Such B-cell activation may be considered to be polyclonal, independent of the presence of parasite antigens for its expression in vivo. Indeed, parasite antigens are needed to prime TH2 T cells in vivo and to stimulate them in vitro but are not necessary for the induction of B-cell activation and differentiation in vivo. Taken together, the above experimental data show that TH2 cells may mimic several features of the immunopathology in mice chronically infected with T. cruzi including (1) mediation of a DTH reaction leading to tissue mononuclear infiltrates; and (2) mediation of B cell helper function -- leading to polyclonal activation with an isotypic pattern similar to that of chronic infection with a majority of IgG2 isotypes (l~'Imnerln I.ima pt al__ IQR¢~_ ;.
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.
.
r
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
i
.
.
.
expansion of CD5 + B cells during the acute stage of infection may have a negative effect on the triggering of THI cells, allowing TH2 ceils to develop (Minoprio, this Forum). In a vaccination perspective, it is of overwhelming importance to understand the mechanisms by which the parasite commits the immune system to massive polyclonal activation. This may be done directly by a specific parasite molecule or indirectly by a factor from infected cells, such as a cytokine from mononuclear cells infected by amastigotes. The failure to sustain a permanent polyclonal activation and the lack of an inflammatory pathology with killed parasites, favours the second hypothesis. The challenge posed by Chagas' disease is to identify the molecules and cells responsible for the immunopathology. We have to define molecules (from the parasite or cytokines) and cells (from the host immune system) which trigger early polyclonal activation. In this context, it will be important to demonstrate clearly the relationship between this polyclonal activation and the later chronic pathology.
.
w e have no clear explanation for the unusual characteristics of this 7". cruzi-specific TH2 line which has the lymphokine secretion profile of a TH2 subset but the ability to mediate DTH usually found in the TH 1 subset (Cher and Mossman, 1987; Mossman et aL, 1987). The possibility of subsets existing within TH1 or TH2 cannot be excluded (Wong et al., 1988).
Recently, Fiorentino et al. (1989) have described a lymphokine (IL-10) secreted by TH2 cells that inhibits the proliferation of THI cells. It will be interesting to investigate the secretion of IL-10 by the T. cruzi-specific TH2 cell line and to look for the presence or absence of THI in vivo during all stages of infection. The
References Andrade, Z.A. (1983), Mechanismsof myocardial damage in Trypanos6ma cruzi infection, in "Cytopathology of parasitic disease" (Ciba Foundation symposium 99) (pp. 214-233). Pitman Books, London. Ben Younes-Chennoufi,A., Said, G., Eisen, H., Durand, A. & Hontebeyrie-Joskowicz, M. (1988a), Cellular immunity to Trypanosoma cruzi is mediated by helper T cells (CD4+). Trans. roy. Soc. trop. Med. Hyg., 82, 84-89. Ben Younes-Chennoufi, A., Hontebeyrie-Joskowicz, M., Tricottet, V., Eisen, H., Reynes, M. & Said, G. (1988b), Persistence of Trypanosoma cruzi antigens in the inflammatory lesions of
IMMUNE RESPONSE IN CHAGAS" DISEASE chronically infected mice. Trans. roy. Soc. trop. Med. Hyg., 82, 77-83. Burgess, D.E., Kuhn, R.E. & Carlson, K.S. (1981), Induction of parasite-specific helper T lymphocytes during Trypanosoma cruzi infections in mice. J. Immunol., 127, 2092-2095. Cher, D.J. & Mossman, T.R. (1987), Two types of murine helper T cell clone-II. Delayed-type hypersensitivity is mediated by THI clones. J. lmmunol., 138, 3688-3692. Curotto de Lafaille, M.A., Barbosa de Oliveira, L.C., Lima, G.C. & Abrahamson, I.A. (1990), Trypanosoma cruzi: Maintenance of parasite-specific T-cell responses in lymph nodes during the acute phase of infection. Exp. Parasit., 70, 161-174. D'Imperio Lima, M.R., Eisen, H., Minoprio, P., Joskowicz, M. & Coutinho, A. (1986), Persistence of polyclonal B-cell activation with undetectable parasitemia in late stages of experimental Chagas' disease. J. lmmunoL, 137, 353-356. Fiorentino, D., Bond, M. & Mossman, T. (1989), Two types of helper T cells, m IV. Th2 clones secrete a factor that inhibits cytokine production by Thl clones. J. exp. Med., 170, 2081-2092. Gonzalves da Costa, S.C., Lagrange, P.H., Hurtrel, B., Kerr, I. & Alencar, A. (1984), Role of T lvmnhr~r.wtpc in th,~ r ~ ; c t ~ . , - ~ ~ " d
immunopathology of experimental Chagas' disease. Ann. Immunol. (Inst. Pasteur), 135 C, 317-332. Hontebeyrie-Joskowicz, M., Said, G., Milon, G., Marchal, G. & Eisen, H. (1987), L3T4 + T cells able to mediate parasite-specific delayedtype hypersensitivity play a role in the pathology of experimental Chagas' disease. Europ. J. Immunol., 17, 1027-1033. Kierszenbaum, F. & Pienkowski, M. (1979), Thymus-dependent control of host defense mechanisms against Trypanosoma cruzi. Infect. Immun., 24, 117-121. Krettli, A.U. & Brener, Z. (1976), Protective effects of specific antibodies in Trypanosoma cruzi infections. J. lmmunol., 116, 755-760. Laguens, R.P., Cabeza Meckert, P., Chambo, G. & Gelpi, R.J. (1981), Chronic Chagas' disease in the mouse. -- II. Transfer of the heart disease by means of im-
munocompetent cells. Medicina (Buenos Aires), 41, 40-43. Laguens, R.P., Cabeza Meckert, P. & Chambo, J.G. (1988), Antiheart antibody-dependent cytotoxicity in the sera of mice chronically infected with Trypanosoma cruzi. Infect. Immun., 56, 993-997. Lowy, I., Joskowicz, M. & Theze, J. (1982), Characterization of suppressor cells regulating in vitro expression of lgG2a and IgG2b antibody responses. J. Immunol., 128, 768-773. Martins, M.S., Hudson, L., Krettli, A.U., Cancado, J.R. & Brener, Z. (1985), Human and mouse sera recognize the same polypeptide associated with immunological resistance to Trypanosoma cruzi infection. Clin. exp. Immunol., 61,343-350. Mesri, E.A., Levitus, G., HontebeyrieJoskowicz, M., Dighiero, G., Van Regenmortel, M.H.V. & Levin, M.J. (1990), Major Trypanosoma cruzi antigenic determinant in Chagas' heart disease shares homology with the systemic lupus erythematous ribosomal P protein epitope. J. clin. Microbiol., 28, 1219-1224. Minoprio, P., Eisen, H., Forni, L., D'lmperio Lima, M.R., Joskowicz, M. & Coutinho, A. (1986), Polyclonal lymphocyte responses to murine T. cruzi infection. I. Quantitation of both T and B responses. Scand. J. Immu•ol., 24, 661-668. ...... ,-,v,,,-,, P., t~,~¢,, ra., Joskowicz, M., Pereira, P. & Coutinho, A. (1987), Suppression of polyclonal antibody production in Trypanosoma cruzi-infected mice by treatment with anti-L3T4 antibodies. J. lmmunol., 139, 545-550. Mossman, T.R., Cherwinski, H., Bond, M.W., Giedlin, M.A. & Coffman, R.L. (1986), Two types of murine helper T cell clone. -I. Definition according to profiles of lymphokine activities and secreted proteins. J. Immunol., 136, 2348-2355. Nickell, S.P., Gebremichael, A., Hoff, R. & Boyer, M.H. (1987), Isolation and functional characterization of murine T-cell lines and clones specific for the protozoan parasite Trypanosoma cruzi. J. lmmunol., 138, 914-921. Plata, F., Milon, G., Garcia-Pons, F. & Marchal, G. (1986), Selective suppression of tumour-immune cytolytic T lymphocytes in mice with chronic Trypanosoma cruzi
143
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