Cellular immune response to acetylcholine receptors in murine experimental autoimmune myasthenia gravis: inhibition with monoclonal anti-I-A antibodies

CD4 costimulation is not required in a novel LPS-enhanced model of myasthenia gravis

The potential of lipopolysaccharide (LPS) to induce antigen-specific B cell responses to acetylcholine receptor (AChR) in myasthenia gravis (MG) was evaluated in wild type (WT) and CD4-/- C57BL/6 mice. The WT mice immunized with AChR in LPS developed an MG-like disease (LPS-EAMG) similar to that induced by immunization with AChR in complete Freund's adjuvant (CFA-EAMG). CD4-/- mice were resistant to CFA-EAMG but susceptible to LPS-EAMG. LPS abrogated EAMG resistance in CD4-/- mice by increasing high-affinity anti-AChR IgG2b in sera and enhancing immune complex deposition in muscle.

Suppression of experimental myasthenia gravis by monoclonal antibodies against MHC peptide region involved in presentation of a pathogenic T-cell epitope

We have prepared monoclonal antibodies (mAbs) against an antigen-binding region of I-A, region 62-76 of I-Abeta(b), which is involved in the T-cell participation in the pathogenesis of EAMG. The mAbs reacted with its parent molecules and inhibited the proliferation of disease-related T-cells. Passive transfer of these mAbs suppressed the occurrence of clinical EAMG, which was accompanied by decreased T-cell and Ab responses to tAChR. The results indicated that blocking the function of disease-related MHC by targeting a disease-associated region on MHC molecules could be an effective, straightforward and feasible strategy for immunointervention in MG.

Myasthenia gravis patients with thymus hyperplasia and myasthenia gravis patients with thymoma display different HLA associations

Thirty myasthenia gravis (MG) patients (9 with thymoma, 12 with thymus hyperplasia and 9 with thymic atrophy) and 181 Norwegian healthy controls were serologically typed for HLA-A, -B and -DR antigens and genomically typed for HLA-DQA1 and HLA-DQB1 alleles by probing in vitro amplified DNA with sequence-specific oligonucleotides. In patients with thymus hyperplasia the frequency of the DQB1*0201 allele was increased compared to controls (RR = 3.5, p less than 0.05), whereas among the patients with thymoma this allele was not observed (RR = 0.06, p less than 0.01). The frequencies of HLA-B8, -DR3 and -DQA1*0501, which are in strong linkage disequilibrium with DQB1*0201, were increased in patients with hyperplasia and reduced in patients with thymoma. The data suggest that different HLA genes predispose to two different forms of MG.

Modulation of low-dose streptozotocin-induced diabetes in mice by administration of antibodies to I-A, I-E and I-J determinants

In male mice of strains C3H and C57BL/6 an experimental immune-mediated diabetes can be induced by multiple low doses of streptozotocin. The delay and partial suppression of hyperglycaemia after anti-I-A monoclonal antibody administration was dose dependent. Even saturation levels of anti-I-A did not cause complete protection from diabetes development. Administration of anti-I-E monoclonal antibody also significantly delayed the onset of hyperglycaemia. Surprisingly, the combined treatment with anti-I-A and anti-I-E did not result in better protection from diabetes. Thus, there is an I-A and I-E independent component of the disease. Furthermore, there is no restriction to either I-A or I-E. Anti-I-A was only effective when given at the beginning of the experiment, which implies that I-A molecules have a primary function during the induction of diabetes. The contribution of I-J to the disease process is different. Administration of a polyspecific alloantiserum to I-J almost completely prevented hyperglycaemia. Injections of monospecific antibodies to I-J determinants enhanced hyperglycaemia, especially when given after the induction of diabetes. This indicates that I-J is involved in initial as well as in later stages of the disease process.

Involvement of HLA in clinical courses of myasthenia gravis

The relationship between the histocompatibility leukocyte antigen (HLA) phenotypes and the clinical course of myasthenia gravis (MG) was studied in 53 Japanese patients with MG. The frequency of HLA-DRw9 antigen was high in the MG patients who did not need immunosuppressive therapy but only anticholinesterase agents (RR = 4.52; CP less than 0.02), who achieved remission of the disease (RR = 2.98; CP less than 0.05) or who showed a decrease in AChR antibody (Ab) titer (RR = 6.32; CP less than 0.0002), whereas the frequency of HLA-DRw8 antigen was increased in MG patients who underwent immunosuppressive therapy (RR = 4.03; CP less than 0.01), who did not have remission (RR = 4.75; CP less than 0.1) or who showed an increase in AChR Ab titer (RR = 6.48; CP less than 0.01). These data suggest that immunogenetic heterogeneity in MG might be reflected in its clinical course.

Fc gamma receptors and HLA-DR antigens on thymus cells in myasthenia gravis

Receptors for the Fc part of IgG (Fc gamma R) and HLA-DR antigens were detected in thymus tissue from patients with myasthenia gravis (MG) using monoclonal antibodies (B1D6 and OKIa1) in indirect immunofluorescence. The amount of Fc gamma R and HLA-DR antigens was increased on epithelial reticular cells and on interdigitating reticular cells in hyperplastic thymus as compared to normal thymus. In thymomas from MG patients the neoplastic epithelial cells expressed Fc gamma R, whereas only a few cells had HLA-DR antigens. Neither thymocytes nor B lymphocytes in the hyperplastic thymuses and in the thymomas were stained by B1D6.

Characterization of the in vitro murine T-cell proliferative responses to murine and human thyroglobulins in thyroiditis-susceptible and -resistant mice

The in vitro proliferative response to autoantigenic mouse thyroglobulin (MTg) of lymph node cells (LNC) from thyroiditis-susceptible (high-responder) CBA/J (H-2k) mice was further characterized. The relatively weak response was enhanced by adding irradiated spleen cells from normal syngeneic mice to cultures of responding LNC. Furthermore, the adjuvant used for immunization was found to influence the magnitude of the response. Results of experiments varying both the adjuvant and the route of immunization (footpad versus subcutaneous) demonstrated that marked proliferative response to MTg in vitro was not necessarily a predictor of the severity of disease. However, the capacity to proliferate in response to MTg correlated with disease susceptibility, as reported previously. The response to MTg was dependent on Thy-1+, Lyt-1+2- cells and was inhibited by monoclonal I-A antibodies. Thus, proliferation is mediated by T cells of the helper/amplifier phenotype recognizing the autoantigen in association with Ia molecules. The determinants on human thyroglobulin (HTg) and MTg stimulating the proliferative responses of LNC from thyroiditis-susceptible and thyroiditis-resistant (low-responder) BALB/c (H-2d) mice were found to differ. Cells from resistant mice proliferated only in response to foreign determinants on HTg and not to shared or mouse-specific epitopes of MTg, whereas susceptible mice had T cells reactive to shared determinants expressed on MTg and HTg as well as to foreign determinants on HTg.

Mutation at I-A beta chain prevents experimental autoimmune myasthenia gravis

Immune response (Ir) gene(s) at the I-A subregion of the mouse H-2 complex influence susceptibility to experimental autoimmune myasthenia gravis (EAMG). To determine the importance of the Ir gene product, the Ia antigens, in EAMG pathogenesis, we studied the degree of EAMG susceptibility of an I-A mutant strain, the B6.C-H-2bm12 (bm12), and its parent B6/Kh. According to the cellular, humoral, biochemical, and clinical manifestations of EAMG, the I-A mutation converted an EAMG susceptible strain (B6/Kh) into a relatively resistant strain (bm12). The relative resistance to EAMG induction in bm12 may be due to the lack of Ia.8 and/or Ia.39 determinants and/or quantitative expression of Ia antigens.