B7-1 costimulatory molecule is critical for the development of experimental autoimmune myasthenia gravis

Following immunization with acetylcholine receptor (AChR), MHC class II-restricted, AChR-specific CD4 cell activation is critical for the development of experimental autoimmune myasthenia gravis (EAMG) in C57BL/6 mice. To study the contributions of B7-1 and B7-2 costimulatory molecules in EAMG, B7-1, B7-2, and B7-1/B7-2 gene knockout (KO) mice were immunized with Torpedo AChR in CFA. Compared with wild-type C57BL6 mice, B7-1 and B7-1/2 KO mice were resistant to EAMG development. B7-1 KO mice had reduced anti-AChR Ab compared with C57BL/6 mice. However, neither B7-1 nor B7-2 gene disruption impaired AChR-induced or dominant alpha(146-162) peptide-induced in vitro lymphoproliferative responses. Blocking of the B7-1 or B7-2 molecule by specific mAbs in vivo led to a reduction in the AChR-specific lymphocyte response, and the reduction was more pronounced in mice treated with anti-B7-2 Ab. The findings implicate B7-1 molecules as having a critical role in the induction of EAMG, and the resistance of B7-1 KO mice is associated with suppressed humoral, rather than suppressed AChR-specific, T cell responses. The data also point to B7-2 molecules as being the dominant costimulatory molecules required for AChR-induced lymphocyte proliferation.

Role of IL-5 during primary and secondary immune response to acetylcholine receptor

To analyze the role of the Th2 cytokine interleukin-5 (IL-5) in experimental autoimmune myasthenia gravis (EAMG) pathogenesis, we induced clinical EAMG in C57BL/6 and IL-5 gene-knockout (KO) mice in the C57BL/6 background. IL-5 KO mice had a significantly reduced incidence and severity of EAMG. Despite their increased resistance to EAMG, IL-5 KO mice displayed intact secondary antibody and lymphoproliferative responses to acetylcholine receptor (AChR) after immunization with this molecule. However, the relative resistance of IL-5 KO mice was associated with a reduced primary lymphocyte response to AChR, and reduced C3 levels in muscle extracts compared to those in C57BL/6 mice.

HLA-DQ6 transgenic mice resistance to experimental autoimmune myasthenia gravis is linked to reduced acetylcholine receptor-specific IFN-gamma, IL-2 and IL-10 production

To comprehend the reduced susceptibility of HLA-DQ6 transgenic mice in comparison with HLA-DQ8 mice, to experimental autoimmune myasthenia gravis (EAMG), we immunized them with acetylcholine receptor (AChR) and examined in vitro, the proliferative and cytokine responses to AChR. When immunized with AChR and examined for AChR-specific lymphocyte responses to AChR, EAMG-resistant DQ6 mice exhibited significantly reduced in vitro lymphoproliferative and cytokine responses to AChR, compared to DQ8 mice. The differences in susceptibility were not linked to a difference in peptide recognition by AChR-specific lymphocytes. AChR T cell epitope mapping showed that both DQ6 and DQ8 responded to the same epitopes, although to varying degrees. Resistance of DQ6 transgenic mice to EAMG was linked to a dramatic suppression of AChR-specific IFN-gamma, IL-2 and IL-10 productions by AChR-primed lymph node cells.