Suppression of experimental autoimmune encephalomyelitis by the oral administration of myelin basic protein

The oral administration of myelin basic protein (MBP) to Lewis rats prior to an encephalitogenic challenge resulted in total inhibition or a significant delay in the onset of experimental autoimmune encephalomyelitis (EAE). In vitro lymphocyte proliferative responses to MBP were significantly decreased in MBP-fed rats when compared with vehicle-fed controls. Suppression of EAE and in vitro proliferative responses to MBP were observed to be antigen specific, since oral feeding of a control protein exerted no suppressive effect. Moreover, the specificity of MBP-induced oral tolerance was shown to be species specific, since feeding guinea pig MBP (GPMBP) or human MBP (HuMBP) induced protection only against a GPMBP or HuMBP challenge, respectively. Conversely, Lewis rats could not be orally tolerized to the self antigen rat MBP.     

Oral tolerance in experimental autoimmune encephalomyelitis. III. Evidence for clonal anergy.

We have recently reported that experimental autoimmune encephalomyelitis (EAE) can be suppressed by the oral administration of myelin basic protein (MBP). The oral introduction of 20 mg MBP together with a trypsin inhibitor results in inhibition of EAE clinical signs, decreased CNS histopathologic changes and dramatically reduced MBP-specific proliferative responses in fed and challenged Lewis rats. In the present study, we have investigated the mechanism underlying MBP-induced oral tolerance in EAE. Neither lymphoid cells (lymph node cells, spleen cells, Peyer's patch lymphocytes, thymocytes) nor humoral elements derived from tolerant donors were capable of transferring the tolerance to naive recipients. Moreover, lymphoid cells obtained from orally tolerant donors exhibited a marked decrease in their capacity to transfer EAE to naive recipient rats, even after in vitro activation with MBP or Con A. We observed that EAE could be readily transferred into orally tolerant rats using MBP-specific encephalitogenic T cell lines. In vitro cell mixing studies showed that the proliferation of lymphocytes from MBP-sensitized donors was not inhibited by the addition of lymphoid cells from tolerant donors, arguing against the role of a suppressor cell. Investigation of MBP-stimulated lymphokine production showed that both IL-2 and IFN-gamma levels were substantially decreased in spleen and lymph node cell cultures from MBP-fed rats compared to vehicle-fed control animals. Furthermore, limiting dilution analyses revealed that MBP-fed rats exhibited a profound decrease in MBP-reactive, IL-2-secreting lymphocytes relative to control animals. Thus, because lymphocytes from MBP-fed rats neither proliferate nor secrete IL-2 or IFN-gamma in response to MBP and we can find no compelling evidence for the role of suppressor cells, we propose that the oral administration of MBP results in a state of clonal anergy.     

Experimental allergic encephalomyelitis: clinical disease and enhanced cellular transfer in the absence of lymphocyte proliferative responses against syngeneic MBP

Experimental allergic encephalomyelitis (EAE) was induced in Lewis rats using several different immunization protocols, and draining lymph node cells from these animals were assayed for proliferation against heterologous, homologous, and syngeneic MBP, and syngeneic spinal cord. Proliferative responses were largely stimulated by nonsyngeneic antigenic determinants and correlated better with the antigen used to induce EAE than with signs of autoimmune disease. Lymph node cells from rats immunized with either guinea pig spinal cord or syngeneic MBP did not proliferate measurably when restimulated in vitro with syngeneic MBP, yet lymphoid cells from these animals were enhanced in their capacity to transfer EAE following in vitro stimulation with syngeneic MBP.     

Suppression of experimental autoimmune encephalomyelitis by oral administration of myelin basic protein. III. Synergistic effect of lipopolysaccharide.

Oral administration of myelin basic protein (MBP) suppresses experimental autoimmune encephalomyelitis (EAE) in Lewis rats immunized with MBP in Freund's adjuvant. The immunomodulator bacterial lipopolysaccharide (LPS) when given orally in conjunction with MBP enhances the protective effects of MBP feeding in EAE. This synergy was achieved only following oral administration of LPS but not following subcutaneous injection. In contrast, subcutaneous administration of LPS abrogated oral tolerance. A synergism between oral LPS and MBP was also demonstrated for antigen-specific suppression of delayed type hypersensitivity (DTH) responses. Antibody responses to MBP were suppressed by oral administration of MBP but not by MBP plus LPS. The lipid A moeity of LPS mimicked the effects of LPS on disease protection and DTH suppression. These data demonstrate that adjuvants can enhance the induction of antigen-specific oral tolerance for suppression of cell-mediated experimental autoimmune responses.     

Induction of IL-10-producing CD4+CD25+ T cells in animal model of collagen-induced arthritis by oral administration of type II collagen

Induction of oral tolerance has long been considered a promising approach to the treatment of chronic autoimmune diseases, including rheumatoid arthritis (RA). Oral administration of type II collagen (CII) has been proven to improve signs and symptoms in RA patients without troublesome toxicity. To investigate the mechanism of immune suppression mediated by orally administered antigen, we examined changes in serum IgG subtypes and T-cell proliferative responses to CII, and generation of IL-10-producing CD4+CD25+ T-cell subsets in an animal model of collagen-induced arthritis (CIA). We found that joint inflammation in CIA mice peaked at 5 weeks after primary immunization with CII, which was significantly less in mice tolerized by repeated oral feeding of CII before CIA induction. Mice that had been fed with CII also exhibited increased serum IgG1 and decreased serum IgG2a as compared with nontolerized CIA animals. The T-cell proliferative response to CII was suppressed in lymph nodes of tolerized mice also. Production of IL-10 and of transforming growth factor-beta from mononuclear lymphocytes was increased in the tolerized animals, and CD4+ T cells isolated from tolerized mice did not respond with induction of IFN-gamma when stimulated in vitro with CII. We also observed greater induction of IL-10-producing CD4+CD25+ subsets among CII-stimulated splenic T cells from tolerized mice. These data suggest that when these IL-10-producing CD4+CD25+ T cells encounter CII antigen in affected joints they become activated to exert an anti-inflammatory effect.     

The thymus plays a role in oral tolerance in experimental autoimmune encephalomyelitis

The oral administration of myelin proteins has been used for the successful prevention and treatment of experimental autoimmune encephalomyelitis (EAE). We questioned whether the thymus was involved in oral tolerance. In this study, euthymic myelin basic protein (MBP) TCR transgenic mice are protected from EAE when fed MBP but are not protected when thymectomized. Similarly, in a cell transfer system, T cell responses to OVA measured in vivo were suppressed significantly only in the OVA-fed euthymic mice but not in the thymectomized mice. We observed that the absence of the thymus dramatically enhanced the Th1 response. We explored three alternatives to determine the role of the thymus in oral tolerance: 1) as a site for the induction of regulatory T cells; 2) a site for deletion of autoreactive T cells; or 3) a site for the dissemination of naive T cells. We found that Foxp3(+)CD4(+)CD25(+) T cells are increased in the periphery but not in the thymus after Ag feeding. These CD4(+)CD25(+) T cells also express glucocorticoid-induced TNFR and intracellular CTLA4 and suppress Ag-specific proliferation of CD4(+)CD25(-) cells in vitro. The thymus also plays a role in deletion of autoreactive T cells in the periphery following orally administered MBP. However, thymectomy does not result in homeostatic proliferation and the generation of memory cells in this system. Overall, the oral administration of MBP has a profound effect on systemic immune responses, mediated largely by the generation of regulatory T cells that act to prevent or suppress EAE.     

Suppression of experimental autoimmune encephalomyelitis by oral administration of myelin basic protein and its fragments

We report that experimental autoimmune encephalomyelitis, a T cell-mediated autoimmune disease studied as a model for multiple sclerosis, can be suppressed in Lewis rats by the oral administration of myelin basic protein (MBP). Both the clinical and histopathologic manifestations of the disease were suppressed in a dose-dependent manner. In addition, proliferative responses to MBP and, to a lesser extent, serum levels of anti-MBP antibody were suppressed by feeding MBP. Suppression of clinical and histologic disease was observed whether animals were fed MBP before or after disease induction, although suppression was more complete when rats were fed before immunization. Disease was also suppressed by the oral administration of either encephalitogenic or nonencephalitogenic fragments and decapeptides of the MBP molecule, with more complete suppression observed when nonencephalitogenic fragments were fed, suggesting that suppressor determinants exist in the MBP molecule distinct from the encephalitogenic region. The oral administration of a non-disease-inducing portion of an autoantigen represents an antigen-specific method by which an experimental autoimmune disease can be immunoregulated.     

Suppression of experimental autoimmune uveitis in rats by the oral administration of the uveitopathogenic S-antigen fragment or a cross-reactive homologous peptide.

The oral administration of S-antigen fragment (a synthetic peptide designated as peptide M and known to be uveitopathogenic for rat, guinea pig, and monkey) to Lewis rats prior to challenge with an emulsion of peptide M and CFA resulted in either a total or partial suppression of experimental autoimmune uveitis (EAU), a T cell-mediated autoimmune disease studied as a model for human uveitis and experimental autoimmune pinealitis (EPA). Both the clinical and histopathologic manifestations of the disease were suppressed in a dose-dependent manner. Pinealitis associated with EAU was also suppressed by the oral administration of peptide M. Additionally, ingestion of a fragment of baker's yeast (Saccharomyces cerevisiae) histone H3, which has five consecutive amino acids identical to peptide M and which has been found to be uveitopathogenic in Lewis rats, induced tolerance to either peptide M or synthetic histone H3 peptide. In addition, the proliferative response to peptide M was inhibited in peptide M-fed rats. The suppression of EAU and in vitro lymphocyte proliferative responses to peptide M were observed to be antigen specific, since oral feeding of a control protein (BSA) exerted no suppressive effect. Furthermore, the T cells isolated from the spleen and lymph nodes of animals rendered tolerant by oral administration of peptide M can transfer protection against EAU adoptively. These results demonstrate that the oral administration of an autoantigen or its homologous peptide initiates an antigen-specific cellular mechanism which may ameliorate EAU.     

The role of myelin lipids in experimental allergic encephalomyelitis. III. Transfer of suppression from guinea pigs recovering from EAE, induced by myelin basic protein--galactocerebroside complexes

Juvenile strain 13 guinea pigs were immunized with myelin basic protein (MBP) combined with galactocerebrosides (MBP + GC) or with total myelin lipids without GC [MBP + (TL-GC)] in CFA. Control animals received dinitrophenylated-ovalbumin (DNP-OA) in CFA, CFA or IFA alone. The animals injected with MBP + GC showed a higher rate of recovery from the first EAE episode (83%) than those treated with MBP + (TL-GC) (50%). With the exception of the group treated with IFA alone, all animals were refractory to EAE following rechallenge with MBP in CFA 90 days after the first exposure. The in vitro proliferative response to MBP, of peripheral blood lymphocytes (PBLs) derived from guinea pigs freshly sensitized to MBP in CFA, was drastically suppressed in the presence of PBLs from animals injected with MBP + GC. Upon transfer to normal syngeneic recipients, spleen cells from MBP + GC-treated animals completely suppressed the clinical and histological manifestations of EAE following recipient challenge with MBP in CFA. Cell-free supernatants from PBLs and spleen cells of strain 13 guinea pigs treated with MBP + GC inhibited lymphocyte proliferation to MBP, of allogeneic responder cells, and spleen cell supernatants completely suppressed the induction of EAE upon transfer to allogeneic recipients. Suppression could not be transferred with cells from other treated groups. These results suggest that animals immunized with MBP + galactocerebrosides in CFA develop suppressor cells that may be in part responsible for the recovery from the first EAE episode and for protection against rechallenge with MBP in CFA. Their cell-free supernatants act in an MHC-nonrestricted fashion. These results do not rule out an additional protective mechanism since all animals exposed to CFA were refractory to rechallenge despite lack of demonstrable suppressor cell activity.     

Rapid depletion of peripheral antigen-specific T cells in TCR-transgenic mice after oral administration of myelin basic protein

In myelin basic protein (MBP)-specific TCR-transgenic (Tg) mice, peripheral T cells express the Valpha2.3/Vbeta8.2-Tg TCR, demonstrate vigorous proliferative responses to MBP in vitro, and can exhibit experimental autoimmune encephalomyelitis (EAE) within 5 days of pertussis toxin injection. We explored the effects of oral administration of MBP on the cellular trafficking of the MBP-specific TCR-Tg cells and the ability of oral MBP to protect Tg mice from EAE. Tg mice were fed MBP, OVA or vehicle and sacrificed at various times after feeding. An immediate and dramatic decrease in Valpha2.3/Vbeta8.2(+)-Tg cells was observed in the periphery within 1 h after feeding. By 3 days after feeding, the percentage of Tg cells increased to near control levels, but decreased again by 10 days. When MBP or vehicle-fed Tg mice were challenged for EAE at this point, disease was severe in the vehicle-fed mice and reduced in the MBP-fed mice over the 40-day observation period. In vitro studies revealed a biphasic pattern of MBP proliferative unresponsiveness and an induction of Th1 cytokines. Immunohistochemical staining showed that the number of Tg cells found in the intestinal lamina propria increased dramatically as the number of Tg cells in the periphery decreased. There was no apparent proliferation of Tg cells in the lamina propria, indicating that Tg cells trafficked there from the periphery. Taken together, these results suggest that T cell trafficking into the site of Ag deposition acts to protect the TCR-Tg mouse from EAE.     

Indomethacin augments in vitro proliferative responses of Lewis rat lymphocytes to myelin basic protein. Implications for experimental autoimmune encephalomyelitis

Indomethacin (IM), a specific inhibitor of prostaglandin (PG) synthesis, and PGE2 were studied in terms of their ability to modulate in vitro immune responses associated with experimental autoimmune encephalomyelitis (EAE) in Lewis rats. Lymphoid cells from either the spleens or the draining lymph nodes of myelin basic protein (MBP)-sensitized rats exhibited in vitro immune responses which were enhanced in the presence of IM. Specifically, IM enhanced (i) guinea pig MBP (GPMBP)- and rat MBP (RMBP)-stimulated lymphocyte proliferation, (ii) background proliferation, and (iii) interleukin 2 (IL-2)-stimulated proliferation. Conversely, PGE2 inhibited both GPMBP- and IL-2-stimulated proliferation of MBP-sensitized lymphocytes. Together, these results indicate that PGs secreted by cultured lymphoid cells can directly mitigate MBP- or IL-2-stimulated lymphocyte proliferation. Furthermore, the observation that IM and PGE2 modulate in vitro responses of MBP-specific lymphocytes may provide insight into how the in vivo administration of IM potentiates the severity of EAE (H. Ovadia and P.Y. Paterson, Clin. Exp. Immunol. 49, 386, 1982) and how PGs may be involved in the spontaneous remission of EAE in rats.     

Genetic control of the development of experimental allergic encephalomyelitis in rats. Separation of MHC and non-MHC gene effects

Experimental allergic encephalomyelitis (EAE)-susceptible Lew and EAE-resistant Brown Norway (BN) rats and the corresponding MHC congenic strains were examined for their ability to develop clinical and histologic EAE. The ability of T cells from these animals to proliferate in vitro in response to whole guinea pig (GP) myelin basic protein (MBP), rat MBP, and to the major encephalitogenic peptide of GP MBP 66-88 (GP 68-88) was also assessed. We found that Lewis (Lew) was highly susceptible and showed good T cell responses to GP, MBP, rat MBP, and GP 68-88. Lew.1N (BN MHC on Lew background) and BN were not susceptible and T cells from these strains showed significant responses to GP MBP, but not to rat MBP or GP 68-88. Although BN.B1 (Lew MHC on BN background) was not susceptible to actively induced EAE, MBP-specific Lew T cells could transfer severe disease to BN.B1. BN.B1 T cells showed responses to GP-MBP, rat MBP, and GP 68-88 and, when transferred to naive BN.B1 or Lew, induced only mild clinical EAE in both strains. Increasing the number of T cells from BN.B1 had no effect on the severity of clinical symptoms in either recipient, suggesting some deficiency in the T cell repertoire that is necessary for induction of severe EAE. These results suggest that 1) the T cell response to rat MBP and GP68-88 (but not to sites other than 68-88 in GP MBP) is necessary for susceptibility to EAE; 2) the ability to respond to both rat MBP and GP 68-88 is determined by the MHC gene products on APC; and 3) given a permissive MHC, the T cell response that results in EAE is influenced by non-MHC genes.     

Major histocompatibility complex restriction of T-cell responses to varicella-zoster virus in guinea pigs.

Varicella-zoster virus (VZV), adapted to grow in guinea pig fibroblasts, was injected subcutaneously into Hartley, strain 2, and strain 13 guinea pigs. Serum immunoglobulin G antibodies were detected 2 weeks later, and T-cell proliferative responses by blood lymphocytes were found 3 weeks after injection. The proliferating cells bound the 155 antibody, which defines a CD4-like subset of guinea pig T lymphocytes. VZV-infected fibroblasts of human, Hartley, and strain 13 origin elicited equivalent amounts of proliferation, which was quantitatively greater than that obtained with an extracted VZV antigen. Uninfected (control) human or guinea pig fibroblasts did not elicit T-cell proliferation. The proliferative response to VZV required the presence of autologous (strain 2 or 13) antigen-presenting cells and was blocked by the addition of an anti-class II major histocompatibility complex antibody. Effector cells obtained from in vitro cultures mediated class II-restricted cytotoxicity to L2C cells incubated with VZV. Class I-restricted responses were obtained only by cross-priming strain 2 animals with strain 13 peritoneal exudate cells which had been preincubated with VZV. The data indicate that guinea pigs resemble humans in that class II-restricted T cells with specificity for VZV are more readily cultured from blood than are class I-restricted cells.     

In vivo immunomodulation by monoclonal anti-CD4 antibody. II. Effect on T cell response to myelin basic protein and experimental allergic encephalomyelitis

In vivo administration of anti-CD4 mAb (GK1.5) has been shown to be effective in preventing acute and relapsing experimental allergic encephalomyelitis (EAE). In the present report we have studied the depletion of CD4+ cells by a single dose of GK1.5 on the immune response to myelin basic protein and in the development of EAE. Our studies show that depletion of CD4 cells in mice that had received encephalitogenic CD4+ T cells altered the kinetics of acute and relapsing EAE, but did not prevent disease altogether. The in vitro T cell proliferative response to myelin basic protein in lymph node cells was maintained in the presence of significant depletion of CD4+ cells. These studies indicate that the population of Ag-reactive cells to be large and relatively refractory to antibody therapy. The implication of these results to therapy of human autoimmune disease is discussed.     

Chronic relapsing experimental allergic encephalomyelitis: Identification and dynamics of T and B cells within the central nervous system

Using a monoclonal antibody against guinea pig T cells and anti-guinea pig immunoglobulins, T- and B-cell dynamics were studied by immunofluorescence in situ in the central nervous system (CNS) of animals with untreated and treated chronic relapsing experimental allergic encephalomyelitis (EAE). Treated animals were given a series of injections of either myelin basic protein (MBP) in incomplete Freund's adjuvant (IFA) or MBP and galactocerebroside in IFA. Within the CNS, T and B cells showed distinct distribution patterns in untreated chronic relapsing EAE, similar to that recently described in acute EAE. T cells were predominantly localized within the CNS parenchyma and B cells were mainly found in perivascular areas. B-cell infiltrates were more extensive than in acute EAE and, although most were centered around blood vessels, some were also detectable in the parenchyma. IgG, C₃, and albumin deposits were common. These observations suggest an age-dependent difference in the immune response. In treated chronic EAE, the disease process was apparently arrested and T- and B-cell infiltrates in the white matter were negligible. Therefore, it appears that the present treatment protocol prevents lymphocytes from entering the CNS parenchyma.     

LF 15-0195 inhibits the development of rat central nervous system autoimmunity by inducing long-lasting tolerance in autoreactive CD4 T cells

Experimental autoimmune encephalomyelitis (EAE) is a T cell-dependent autoimmune disease induced in susceptible animals by a single immunization with myelin basic protein (MBP). LF 15-0195 is a novel immunosuppressor that has been shown to have a potent immunosuppressive effect in several pathological manifestations. The purpose of this study was to investigate the effect of this drug on the induction and progression of established rat EAE and to dissect the mechanisms involved. We show that LF 15-0195 administration at the time of MBP immunization reduces the incidence and severity of EAE in Lewis rats. This drug also inhibits ongoing and passively induced EAE, indicating that LF 15-0195 affects already differentiated pathogenic lymphocytes. Compared with lymph node cells from untreated rats, lymphocytes from MBP-immunized rats treated with LF 15-0195 proliferated equally well in response to MBP in vitro, while their ability to produce effector cytokines and to transfer EAE into syngeneic recipients was significantly reduced. This phenomenon is stable and long-lasting. Indeed, neither IL-12 nor repeated stimulation with naive APC and MBP in vitro rendered MBP-specific CD4 T cells from protected rats encephalitogenic. In conclusion, LF 15-0195 treatment suppresses EAE by interfering with both the differentiation and effector functions of autoantigen-specific CD4 T cells.     

Suppression of experimental allergic encephalomyelitis by MBP-coupled lymphoid cells and by MBP-liposomes: a comparison.

In previous experiments, we showed that administration of myelin basic protein (MBP) inserted into phosphatidyl-serine liposomes, to susceptible animals suppressed the clinical manifestations of both acute and chronic-relapsing EAE. In this report we compare the effectiveness of treatment with MBP-liposomes and with MBP-coupled syngeneic spleen cells in EAE protection. Lewis rats treated with 150 micrograms MBP-liposomes or with 160 micrograms (35 x 10(6] MBP-coupled spleen cells, given 7 days before and 7 days after encephalitogenic challenge were equally protected against clinical EAE, when compared to untreated controls. In addition to clinical protection, in vitro proliferative responses of lymphocytes from treated rats were significantly reduced, but delayed hypersensitivity (DTH) reactions remained unaffected. Proliferation of lymphocytes from MBP-sensitized donors was inhibited by the addition of spleen cells but not of lymph node cells from treated donors. The inhibitory effect was observed with spleen cells regardless of whether the donors were treated or not, was antigen nonspecific, and localized in a radio-resistant, adherent cell population. Adoptive transfers of spleen cells from treated donors, after a 48-hr in vitro incubation with concanavalin A, showed that the cells from donors treated with MBP-coupled spleen cells, but not with MBP-liposomes, suppressed the disease in recipients, following challenge with MBP-complete Freund's adjuvant (CFA). These results suggest that two distinct mechanisms operate in the protection by MBP-coupled cells and MBP-liposomes, respectively.     

Antigen-induced suppression of mitogen responses and resistance to experimental autoimmune encephalomyelitis

Random-bred Hartley and inbred Strain 2 and Strain 13 guinea pigs were inoculated for acute experimental autoimmune encephalomyelitis (EAE). Sixty-six percent (69/103) of the Hartleys developed signs of EAE while the remaining 34% (34/103) were resistant. No Strain 2 and all Strain 13 guinea pigs developed EAE. Histologic examination of nervous tissue revealed that susceptible Hartleys and Strain 13 and Strain 2 animals had lesions characteristic of EAE. Tissue from resistant Hartleys showed fewer and less severe changes. Lymphocyte-transformation assays with EAE-inducing and noninducing antigens and T-cell mitogens revealed three different sets of responses in vitro: (i) lymphocytes from all animals responded to mitogens; (ii) lymphocytes from susceptible animals responded to EAE-inducing antigens; and (iii) lymphocytes from resistant Hartleys were suppressed from responding to the mitogens solely by EAE-inducing antigens. Plasmas from all EAE-sensitized animals had equivalent anti-myelin basic proteins (MBP) antibody titers and skin tests of EAE-inoculated Hartleys were all positive for MBP sensitization. Therefore, resistance and reduced histologic changes characteristic of EAE correlated with a disease-specific antigen-induced suppression of lymphocyte responses to T-cell mitogens. This suggests that clinical resistance to EAE in Hartley guinea pigs is mediated by an immunologic suppressor mechanism.     

The suppression of mitogen responses associated with resistance to experimental autoimmune encephalomyelitis requires adherent and T cells

Resistance to experimental autoimmune encephalomyelitis (EAE) in Hartley guinea pigs has previously been reported to be associated with disease-specific antigen-induced suppression of mitogen responses in vitro. The present studies were initiated to investigate the requirement for different cell populations in this suppression. Intact and adherent-cell-depleted cultures of spleen cells from experimental and control animals were incubated with myelin basic protein (MBP), the major antigen of EAE, with the T-cell mitogen concanavalin A (Con A) alone or with Con A in the presence of MBP. In agreement with previous studies, MBP-induced suppression of the Con A response was observed only in cultures derived from resistant animals. In addition, it was observed that this suppression was abrogated by depletion of adherent cells. When cells from resistant and susceptible animals were mixed, suppression occurred only in the presence of nonadherent cells from resistant guinea pigs. Adherent cells from either resistant or susceptible animals functioned equally well. Cultures of purified E-rosette-forming cells (E+) from resistant animals (i.e., T cells) showed no suppression. Similarly, cells from these same animals which were depleted of E+ cells (i.e., non-T cells) did not demonstrate suppression in vitro. Upon reconstitution of spleen cell populations from resistant guinea pigs by mixing E+ and E- cells, suppression was restored. These experiments show that this model of suppression in vitro requires adherent cells as well as T cells and suggests that antigen-induced suppression of mitogen responses is dependent upon a cell-mediated immunologic mechanism.     

Functional heterogeneity among CD4+ encephalitogenic T cells in recruitment of CD8+ T cells in experimental autoimmune encephalomyelitis

Inoculation of Lewis rats with live or attenuated (irradiated or paraformaldehyde-fixed) CD4+ encephalitogenic T cells (S1 line) protects the recipients from transferred experimental autoimmune encephalomyelitis (tEAE) induced by S1 cells. A CD8+ T lymphocyte population specifically activated against the EAE-inducing S1 cells can be readily isolated from the lymphoid organs of pretreated animals. We show, in the present study, that encephalitogenic T cell lines derived from Lewis rats differ in their ability to induce resistance against tEAE in vivo and to stimulate CD8+ cell proliferation in vitro. We also demonstrate that the S19 line of encephalitogenic T cells, in combination with myelin basic protein (MBP), can stimulate CD8+ cell proliferation in vitro. The CD8+ cells generated in this way strongly suppress MBP-specific T cell proliferation in vitro. This combined effect of T cells and MBP was also evident in vivo. Neither S19 cells nor MBP alone induced resistance against S19-mediated tEAE, rather coinjection of these cells and MBP was required. Our results suggest that resistance to EAE is mediated by distinct populations of encephalitogenic T cells that activate Ts cells through different mechanisms. In some instances, both autoreactive T cells and their relevant autoantigen(s) may be needed to activate Ts cells in vivo.