Transient decomplementation of mice delays onset of experimental autoimmune encephalomyelitis and impairs MOG-specific T cell response and autoantibody production.

Multiple sclerosis (MS) is the most common inflammatory and demyelinating disease of the central nervous system. In both MS and its animal model experimental autoimmune encephalomyelitis (EAE), it is thought that infiltrating CD4(+) T cells initiate an inflammatory process and collect other immune effectors to mediate tissue damage. The pathophysiology of the disease however remains unclear. Here we focus on the role of the complement system in the pathomechanism of EAE, employing mice with transiently depleted complement activity achieved by a single injection of cobra venom factor (CVF) 2 days before the induction of the disease. Our results show that in decomplemented C57BL/6 mice immunized with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55, the onset of the disease is significantly delayed. In SJL/J mice which develop a relapsing-remitting form of EAE after injection with proteolipid protein (PLP) peptide 139-151, the attenuation of both phases could be observed in CVF-treated animals. In C57BL/6 mice the level of MOG specific autoantibodies and their complement activating capacity evaluated on day 21 were found significantly reduced in animals transiently decomplemented before induction of the disease. The in vitro response of T cells isolated from the lymph nodes of MOG-immunized animals at the onset of EAE was also investigated. We found that the proliferative capacity of MOG-specific T lymphocytes derived from CVF treated animals is significantly reduced, in agreement with the histology of the spinal cords showing a decreased infiltration of CD4(+) T cells in these mice. Our data suggest, that lack of systemic complement at the time of induction of EAE delays the onset and attenuates the course of the disease most probably via diminishing the response of MOG-specific T cells and production of autoantibodies.