T lymphocyte lines and clones selected against synthetic myelin basic protein 82-102 peptide from Japanese multiple sclerosis patients

Mechanism of natural killer (NK) cell regulatory role in experimental autoimmune encephalomyelitis

The mechanism of natural killer (NK) cell regulatory role in experimental autoimmune encephalomyelitis (EAE) was studied in SJL/J mice. In vivo experiments showed that NK cell depletion by anti-NK1.1 monoclonal antibody treatment enhanced EAE in mice. To investigate the mechanism, we cultured proteolipid protein (PLP)136-150 peptide-specific, encephalitogenic T cell lines, which were used as the NK cell target. Our results show that NK cells exert a direct cytotoxic effect on autoantigen-specific, encephalitogenic T cells. Furthermore, cytotoxicity to PLP-specific, encephalitogenic T line cells was enhanced by using enriched NK cells as effector cells. However, the cytotoxic effect of NK cells to ovalbumin-specific T line cells and ConA-stimulated T cells could also be detected with a lesser efficiency. Our studies indicate that NK cells play a regulatory role in EAE through killing of syngeneic T cells which include myelin antigen-specific, encephalitogenic T cells, and thus ameliorate EAE.

Persistence of immune responses to altered and native myelin antigens in patients with multiple sclerosis treated with altered peptide ligand

Altered peptide ligands (APLs) can modulate responses of T cells to native peptide antigens implicated in the pathogenesis of autoimmune diseases. An APL of the putative target antigen myelin basic protein (MBP) peptide 83-99 has been used in abbreviated clinical trials in patients with multiple sclerosis (MS). Our objective was to assess the long-term persistence, and characteristics, of the APL-induced immune response in such patients. We measured the ex vivo proliferative frequency to the APL and native MBP, the cross-reactivity, and the cytokine production by these lines. We found that a 4- to 16-week course of APL therapy could induce a persistent (2-4.5 year) increase in the frequency of T cells responsive to both the APL and the native MBP in a select number of patients. These T cells produced high levels of IL-5, contrasting with the pretreatment observation that the responses to either antigen were IFNgamma (Th1) dominant. Our results indicate that APL therapy can induce persistent Th2-directed immune deviation. Understanding the impact of such APL-induced immune responses on MS disease activity will require additional clinical trials that incorporate careful monitoring of both clinical and immunological parameters.

Identification of Autoimmune T Cells Among In Vivo Expanded CD25+ T Cells in Multiple Sclerosis

Although clonal expansion of autoimmune T cells has been reported in multiple sclerosis (MS), very limited information is available on specificities, clonal size, or activation state of the expanded clones. Here we address the issue of clonal expansion by using a novel technique demonstrating clonotypes defined by single-strand conformation polymorphism of TCR β-chain cDNAs. Examination of activated T cells (CD3+CD25+) isolated from the peripheral blood of MS revealed limited numbers (20∼82) of expanded clones defined by single-strand conformation polymorphism clonotype. To estimate the Ag specificities of dominant clonotypes in the activated T cells, these samples were examined in parallel with Th1 T cell clones specific for myelin basic protein or proteolipid protein (PLP) derived from the same patients. Analysis of two patients demonstrated that the dominant clonotypes would contain those specific for myelin basic protein or PLP. Although the majority of the clonotypes could be detected only transiently, a PLP95–116-specific clonotype was found to persist for over 1 yr. Thus, single-strand conformation polymorphism clonotype analysis allows us to monitor the kinetics of given T cell clones in vivo and could provide useful information for designing clonotype (Id)-specific manipulation of human diseases such as MS.

Characterization of a human T cell line reactive to a 52 kDa islet protein

A 52 kDa islet protein has recently been identified as the target of autoantibodies in the NOD mouse model of IDDM and humans with IDDM. However, the presence of T cell immunity against the 52 kDa islet protein in IDDM has not been reported. We report the establishment and characterization of a T cell line (19KW) that reacts to purified 52 kDa islet protein (purified p52) from a subject with IDDM. The purified p52 induced a proliferative response as measured by thymidine incorporation in the 19KW T cell line with a stimulating index of up to 48. The proliferative responses were greater with increasing doses of purified p52 (0.1, 0.5, 2.0, and 6.0 microg/well). No reactivity was found to a liver fraction purified in the same manner as 52 kDa protein, BSA, ovalbumin, extracts of rat muscle, fibroblast, adrenal, or pituitary tissue and to a rat exocrine cell tumor. Irradiated PBMC were required as antigen presenting cells (APC) for 19KW reactivity to the purified p52. The addition of anti-HLA DR or anti-HLA DQ antibodies significantly decreased the islet antigen-induced proliferative response. The addition of antibodies to HLA DP and class I MHC had no effect. Flow cytometric analysis revealed that the majority of T cells expressed CD4 and CD45RO molecules. T cell receptors Vbeta6 and Vbeta5.1 were found on 30 and 14% of the CD3+ (T cells) 19KW cells, respectively. In conclusion, a purified p52-reactive human T cell line predominantly consisting of TCR Vbeta6+ and Vbeta5.1+ cells has been established from a subject with IDDM. Reactivity to the purified p52 is antigen dose-dependent, tissue specific, requires irradiated PBMC as antigen presenting cells, and is HLA DR- and HLA DQ-restricted. T cell lines specifically reactive to p52 may be useful for investigating further the role of this antigen in the pathogenesis of IDDM.

A study of human T-cell lines generated from multiple sclerosis patients and controls by stimulation with peptides of myelin basic protein

We generated T-cell lines from the peripheral blood of controls and of patients with multiple sclerosis (MS) by stimulation with overlapping synthetic peptides representing the entire sequences of all four isoforms of human myelin basic protein (MBP). The T-cell lines reacted to a wide range of epitopes in the major isoforms of MBP and to epitopes that were present only in the minor isoforms. Many MS patients and controls had T-cells responding to one or more cryptic MBP epitopes, as indicated by the generation of a peptide-specific T-cell line(s) by stimulation with synthetic peptides but not by stimulation with whole MBP. About one-third of the peptide-generated lines were cytotoxic. Although we have shown that this technique of peptide stimulation is effective in generating human antiviral cytotoxic CD8+ T-cell lines, all the cytotoxic MBP-specific lines generated by this method were predominantly CD4+. Our study did not reveal any significant differences, between MS patients and controls, in reactivity to epitopes within any of the isoforms of MBP.

Myelin basic protein and human coronavirus 229E cross-reactive T cells in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating neurological disease in which autoreactive T lymphocytes sensitized to myelin components of the central nervous system are postulated to contribute to pathogenesis. The possible relevance of molecular mimicry between a human coronavirus and the myelin basic protein component of myelin in the generation of this autoimmune reaction was evaluated. Myelin basic protein- and virus-reactive T-cell lines were established from 16 MS patients and 14 healthy donors and shown to be mostly CD4+. In contrast to healthy donors, several T-cell lines isolated from MS patients showed cross-reactivity between myelin and coronavirus antigens. Overall, 29% of T-cell lines from MS patients (10 donors) but only 1.3% of T-cell lines from normal control subjects (2 donors) showed an HLA-DR-restricted cross-reactive pattern of antigen activation after in vitro selection with either myelin basic protein or human coronavirus strain 229E antigens. Moreover, reciprocal reactivities were only observed in MS patients (4 donors). This establishes molecular mimicry between a common viral pathogen, such as this human coronavirus, and myelin as a possible immunopathological mechanism in MS and is consistent with the possible involvement of more than one infectious pathogen as an environmental trigger of disease.