Suppression of the CD28/B7 pathway reduces the occurrence and development of myasthenia gravis and cytokine levels

Myasthenia gravis (MG) is an antibody-mediated, autoimmune neuromuscular disease. Reports have indicated that the CD28/B7 ligand interactions play a crucial role during primary immune responses. Hence, the aim of the present study was to investigate the possible effects of the CD28/B7 pathway on the occurrence and development of MG and its associated cytokine factors.An experimental autoimmune myasthenia gravis (EAMG) was initially established by immunization of Lewis rats with acetylcholine receptor (AChR) α97-116 peptide. Then the rats were treated with dexamethasone and CTLA4-Ig (used for inhibiting the CD28/B7 pathway). Serum levels of AChR IgG and AChR IgG2b were then detected using ELISA. The clinical features, muscle contraction function, AChR content, expression of CD28, CTLA4, B7.1 and B7.2 in mononuclear cells of peripheral blood and the secretion of cytokines (INF-γ, IL-2, IL-10 and IL-12) in serum of rats were measured. Finally, lymphocyte proliferation upon CTLA4 IgG treatment was examined in vitro.Inhibition of the CD28/B7 pathway and dexamethasone were found to significantly improve clinical symptoms of EAMG rats, reduce serum levels of AChR IgG, AChR IgG2b, INF-γ, IL-2, IL-10 and IL-12, the expression of CD28, CTLA4, B7.1 and B7.2 in mononuclear cells of peripheral blood, and enhance muscle contraction function and AChR content in the muscle in vivo. Meanwhile, CTLA4 IgG could abolish the increased lymphocyte proliferation following AChR stimulation in vitro.Overall, the suppression of the CD28/B7 pathway by CTLA4-Ig can have the potential to retard the occurrence and development of MG.