Immun system occurs from peripheral organs and celular elements including T cells, B cells, mononuclear phagocytes, natural killer (NK) cells. The events that lead to autoimmune disease are not clear. The immune mediated neurologic diseases probably occur the following sequential steps. 1- The breaking of the self tolerance, 2- The processing of the antigen by the antigen presenting cell and antigen recognition by the T-cell receptor complex. 3- Migration of activated T cells from the circulation to the nervous system via adhesion molecules, 4- Tissue injury. Cytokines and lymphokines secreted by the activated T cells and macrophages play a major role as enhancers of the immune response.