Work at the Mayo Clinic, has shown that both immunoglobulin G (IgG) directed against spinal cord antigens and purified polyclonal mouse IgG administered systemically promote extensive remyelination in SJL mice chronically infected with Theiler's virus. In addition, tissue culture studies suggest that IgG directed against CNS components may promote oligodendroglial proliferation and differentiation. Thus, experimental evidence exists for the concept that immunoglobulins may stimulate the proliferation and differentiation of oligodendrocytes. It is possible that myelin components on the surface of oligodendrocytes could function as receptors or components of receptors. Antibodies could mimic endogenous ligands, thereby inducing the proliferation or differentiation of these cells.