Receptors for the Fc part of IgG (FcgammaR) constitute a family of cell-surface molecules expressed on almost every cell of the immune system. They are also present on non-lymphoid cells such as Schwann cells and endothelial cells. By linking humoral and cell-mediated responses, FcgammaR are key in defending against pathogens. Polymorphisms in some FcgammaR genes are associated with infectious and autoimmune diseases. It was found recently that certain FcgammaRIIA and FcgammaRIIIB allotypes are correlated with the disease course of Guillain-Barré syndrome (GBS) and multiple sclerosis (MS). This may imply that clearance of circulating autoantibodies and immune complexes is important in the pathogenesis of these diseases.