Paraneoplastic syndromes of the nervous system

Paraneoplastic syndromes affecting the nervous system are unique among immu ne-mediated disorders in that the trigger of the immune response is known: tumor expression of proteins normally restricted to neurons (or other immun oprivileged sites, such as testis) but ectopically expressed in some cancer s results in an immunological response characterized by high titers of anti bodies targeting the "onconeuronal" antigen. A T-cell response is also elic ited in some paraneoplastic syndromes and may be the cause of neuronal dest ruction. In some instances genes that code for the antigens recognized by t he autoantibodies have been identified, cloned and sequenced. Some of the p roteins so identified are RNA binding proteins but their specific function has not been identified. In some individuals with cancer but no paraneoplas tic syndrome, low titers of antibody can be identified in the serum. Low ti ters of antibody are associated with a better prognosis of the cancer. Expe rimental animals immunized against a paraneoplastic antigen are partially p rotected against tumors that express that antigen.