T cell requirement for experimental allergic encephalomyelitis induction in the rat.

The question of whether a cell-mediated or a humoral mechanism initiates EAE in rats sensitized with BP-CFA was investigated. The requirement of T cells for EAE induction was manifested when Tx, irradiated rats were reconstituted with normal lymphoid cells treated with ATS and then injected with BP-CFA. Neither EAE nor antibody was produced, indicating the T cell dependency of BP specific antibody production. More precise information regarding the role of the T cell in the production of EAE was obtained by means of passive transfer of EAE with sensitized lymphocytes. Thus, transfer of lymphoid cells from rats previously sensitized to BP-CFA into Tx, irradiated rats elicited EAE and antibodies to BP. However, no EAE followed when the transferred cells were first depleted of T cells by treatment with ATS. Nevertheless, ATP pretreatment did not depress the levels of antibody to BP produced in the transfer recipients. The latter finding indicates that the cells from animals sensitized 9 days previously were already committed to the production of antibodies to BP. Therefore, a) T cells are absolutely necessary for induction of EAE and b) antibody detected by antigen-binding is not responsible for the pathogenesis of this disease.     

Experimental allergic encephalomyelitis mediated by murine encephalitogenic T cell lines specific for myelin proteolipid apoprotein

T cell lines specific for bovine myelin proteolipid apoprotein (PLP) were established from SJL/J mice. The line cells bore surface phenotypes of T helper/inducer cells (Lyt-1+, Lyt-2-, L3T4+) and responded well to bovine, rat, and guinea pig PLP but not to myelin basic protein. One line responded to major PLP, and another responded to both major PLP and DM-20, which are the two major intrinsic membrane proteins of the central nervous system (CNS) myelin. Intraperitoneal inoculation of 4 to 30 X 10(6) PLP-activated line cells followed by injection of pertussis vaccine induced acute inflammatory disease of the CNS, with typical clinical signs of EAE mostly in a week in recipient mice that had been treated with low-dose irradiation. Almost all animals recovered completely, and two of the 12 animals relapsed 42 or 75 days after inoculation. The lesions were restricted to the CNS and were characterized by perivascular and parenchymal infiltration of inflammatory cells, fibrin deposit, and demyelination. In the severe lesions, axons were also damaged. These observations suggest that PLP is a definite encephalitogen, and PLP-sensitized effector T cells induce inflammatory demyelination in the CNS.     

Imbalances in T cell subpopulations in multiple sclerosis patients.

Abnormal proportions of a distinct T cell subpopulation able to bind IgG immune complexes (T.G cells) were found in peripheral blood samples from patients with MS. About 50% of the patients examined had an overabundance of T.G cells. The possible role of these cells in the pathogenesis of MS is considered.     

In trans T cell tolerance diminishes autoantibody responses and exacerbates experimental allergic encephalomyelitis

A number of Ag-specific approaches have been developed that ameliorate experimental allergic encephalomyelitis (EAE), an animal model for the human autoimmune disease multiple sclerosis. Translation to humans, however, remains a consideration, justifying the search for more insight into the mechanism underlying restoration of self-tolerance. Ig-proteolipid protein (PLP) 1 and Ig-myelin oligodendrocyte glycoprotein (MOG) are Ig chimeras carrying the encephalitogenic PLP 139-151 and MOG 35-55 amino acid sequence, respectively. Ig-PLP1 ameliorates EAE in SJL/J (H-2(s)) mice while Ig-MOG modulates the disease in C57BL/6 (H-2(b)) animals. In this study, we asked whether the chimeras would suppress EAE in F(1) mice expressing both parental MHC alleles and representing a polymorphism with more relevance to human circumstances. The results show that Ig-MOG modulates both PLP1 and MOG peptide-induced EAE in the F(1) mice, whereas Ig-PLP1 counters PLP1 EAE but exacerbates MOG-induced disease. This in trans aggravation of MOG EAE by Ig-PLP1 operates through induction of PLP1-specific T cells producing IL-5 that sustained inhibition of MOG-specific Abs leading to exacerbation of EAE. Thus, in trans T cell tolerance, which should be operative in polymorphic systems, can aggravate rather than ameliorate autoimmunity. This phenomenon possibly takes place through interference with protective humoral immunity.     

T cell dynamics during induction of tolerance and suppression of experimental allergic encephalomyelitis

The cell dynamics associated with induction of peripheral T cell tolerance remain largely undefined. In this study, an in vivo model was adapted to two-photon microscopy imaging, and T cell behavior was analyzed on tolerogen-induced modulation. FcγR-deficient (FcγR(-/-)) mice were unable to resist or alleviate experimental allergic encephalomyelitis when treated with Ig-myelin oligodendrocyte glycoprotein (MOG) tolerogen, an Ig carrying the MOG35-55 peptide. However, when FcγR(+/+) dendritic cells (DCs) are adoptively transferred into FcγR(-/-) mice, uptake and presentation of Ig-MOG occurs and the animals were able to overcome experimental allergic encephalomyelitis. We then fluorescently labeled FcγR(+/+) DCs and 2D2 MOG-specific TCR-transgenic T cells, transferred them into FcγR(-/-) mice, administered Ig-MOG, and analyzed both T cell-DC contact events and T cell motility. The results indicate that tolerance takes place in lymphoid organs, and surprisingly, the T cells do not become anergic but instead have a Th2 phenotype. The tolerant Th2 cells displayed reduced motility after tolerogen exposure similar to Th1 cells after immunization. However, the Th2 cells had higher migration speeds and took longer to exhibit changes in motility. Therefore, both Th1 immunity and Th2 tolerance alter T cell migration on Ag recognition, but the kinetics of this effect differ among the subsets.     

Experimental allergic encephalomyelitis: activation of suppressor T lymphocytes by a modified sequence of the T effector determinant

Deletion of certain amino acid residues from the amino acid sequence of the encephalitogenic determinant for guinea pigs, H-Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys-OH, destroyed its ability to induce experimental allergic encephalomyelitis (EAE), a cell-mediated autoimmune disease of myelin. The administration of the modified determinant in the form of 4 repeating pentameric sequences, H-(Phe-Ser-Trp-Gln-Lys)4-Gly-OH, activated an antigen-specific T suppressor lymphocyte subset that rendered both presensitized donors and recipients of donor T lymphocytes unresponsive to an encephalitogenic challenge. Treatment of donors or recipients with cyclophosphamide before or after lymphocyte transfer, respectively, obliterated the ability of peptide S42-sensitized T lymphocytes to induce a state of unresponsiveness to an EAE-challenge. The results establish the existence of antigenic determinants for both immunoinduction and immunoregulation of EAE. The immunoregulatory determinant that activates antigen-specific and cyclophosphamide-sensitive suppressor T lymphocyte subset is sequestered within the disease-inducing or T effector determinant.     

Characterization of a T suppressor cell line that downgrades experimental allergic encephalomyelitis in mice.

A T-suppressor (Ts) cell line of CD8 phenotype was isolated from spleens of SJL/J mice that had recovered from experimental allergic encephalomyelitis (EAE) induced by injection of MBP-activated T cells. The Ts cell line inhibited the proliferation of MBP-sensitized T cells in vitro. Addition of recombinant IL-2 enhanced the Ts-mediated suppression. Adoptively transferred Ts line was able to downgrade EAE in mice subsequently challenged with MBP-activated T cells. The mechanism of suppression appeared to involve neither direct cytolysis of the effector T cells nor the production of a soluble suppressor factor. The findings suggest an in vivo role for suppressor T cells in the regulation of EAE.     

Experimental allergic encephalomyelitis: enhancement of cell-mediated transfer by concanavalin A.

Adoptive transfer of experimental allergic encephalomyelitis (EAE) with splenic lymphocytes from Lewis rats sensitized to myelin basic protein (BP) was potentiated by incubation of the cells in vitro with concanavalin A (Con A). Spleen cells of donors which had recovered from EAE also transferred the disease readily after activation by this procedure. In contrast, the transfer of activity of lymph node cells was not altered. We conclude that during the course of EAE a population of T cells with immunologic memory for BP is generated and persists in the spleen. Incubation with Con A activates these cells and results in marked enhancement of their ability to transfer the disease.     

Kinetics and specificity of T and B cell responses in relapsing experimental allergic encephalomyelitis

T and B cell responses to myelin basic protein (MBP) and its relevant peptide fragments were examined throughout the course of MBP-induced relapsing experimental allergic encephalomyelitis (REAE) in (SJL X PL)F1 mice. T cell reactivity, measured by the antigen-driven proliferation of lymph node T cells in vitro, was directed predominantly against the encephalitogenic MBP-P2 peptide (amino acids 1 to 37) at all stages of disease. Levels of responsiveness did not correlate with disease expression, but declined over time to a relapse level that was four- to sixfold lower than that observed during peak acute stage reactivity. Relapse responses were further distinguished by the detection of host I-E restrictions on Lyt-1+ T cell recognition of P2, P2 recognition by acute-stage T cells occurring solely in the context of host I-A molecules. These data imply an increase in the heterogeneity of relapse T cell responses to MBP to include clones restricted by additional class II glycoproteins. A role for additional CNS autoantigens in the stimulation of relapse T cells is also considered. Serum antibody responses to MBP or the P2 fragment fluctuated randomly throughout R-EAE when total antibody activity (IgM plus IgG) was measured. However, analysis of individual isotypes of IgG immunoglobulins revealed an apparent correlation between peak antigen-binding activity and disease expression which may reflect either an effector or regulatory role for humoral immunity in recurrent EAE. Patterns of early antibody reactivity also distinguished F1 mice that developed or failed to develop disease signs after immunization, the latter exhibiting a consistent drop in antigen-binding activity 4 to 5 days before the usual onset of acute-stage paralysis. The results are considered with regard to possible mechanisms of chronic disease regulation in an environment of functional T cell suppression.     

Myelin basic protein and proteolipid protein reactivity of brain- and cerebrospinal fluid-derived T cell clones in multiple sclerosis and postinfectious encephalomyelitis

T cells were directly cloned from autopsied MS brain plaque tissue and reactivity was measured with the major encephalitogenic neuroantigens, myelin basic protein (MBP), and proteolipid protein (PLP). Control clones were simultaneously derived from the blood. The proportion of T4+ and T8+ T cell clones from the brain tissue differed from that of peripheral blood T cell clones derived at the same time, suggesting that the clones were not derived from the peripheral blood. None of 57 brain-derived T cell clones proliferated to either MBP or PLP, although they responded well to PHA and IL 2. An additional 235 clones derived from the cerebrospinal fluid and 126 clones from the peripheral blood of other subjects with multiple sclerosis also did not proliferate to MBP or PLP. In contrast, five of nine T4+ clones from the CSF of a subject with postinfectious encephalomyelitis exhibited low but clear reactivity to human MBP, supporting the possible role of MBP as the target antigen in this disease. These studies, the first to clone T cells directly from MS plaque tissue, suggest that the lack of consistent T cell reactivity to MBP or PLP in the peripheral blood of MS patients does not appear to be secondary to the sequestration of a large number of these cells in the brain.     

Experimental allergic encephalomyelitis mediated by cloned T cells specific for a synthetic peptide of myelin proteolipid protein. Fine specificity and T cell receptor V beta usage.

Proteolipid protein (PLP) is the major protein of central nervous system myelin. SJL (H-2s) mice immunized with a synthetic peptide corresponding to PLP residues 139-151 develop acute EAE. In this study, 6 IAs-restricted, CD4+, TCR alpha beta-bearing T cell clones were derived from SJL/J mice after immunization with this synthetic peptide. The clones responded in in vitro proliferative assays to the whole PLP molecule and to PLP peptide 139-151, but not to irrelevant Ag. They also responded to truncated and overlapping forms of the peptide but five distinct reactivity patterns were observed using these peptides. A panel of anti-TCR V beta mAb and TCR V beta-specific cDNA probes were used to determine the TCR V beta usage of the clones. Five clones were found to use four different V beta (V beta 2, V beta 6, V beta 10, or V beta 17a), whereas the V beta on the sixth clone could not be identified. Five of the clones induced EAE of varying severity upon adoptive transfer into naive syngeneic mice or mice pretreated with irradiation and pertussis and one clone was nonencephalitogenic. The Ag-specific proliferative response of all but the nonencephalitogenic clone could be blocked by an anti-CD4 mAb. Thus, the clones showed differences in their fine specifity, TCR V beta usage, sensitivity to antibody blocking, and encephalitogenic potency. These data demonstrate that the T cell response to the encephalitogenic PLP peptide 139-151 is heterogeneous.