Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that affects multiple organs. Involvement of the central nervous system (CNS) in SLE is called CNS lupus. In the CNS lupus, the disease state of neuropsychiatric manifestations without clear organic abnormalities, that is, acute confusional state, anxiety disorder, mood disorder, psychosis, and cognitive dysfunction, is further classified into neuropsychiatric lupus (NPSLE). Recently, existence of autoantibodies to neuronal cells, called anti-neuronal antibodies, has been reported in NPSLE. Even though they may be related to the pathogenesis and/or diagnosis of NPSLE, further investigations have been hampered because target antigens for the anti-neuronal antibodies have not been identified. Therefore, we here tried to identify the antigens using 2-dimensional electrophoresis and western blotting. We first separated proteins extracted from cultured human neuroblastoma cells (SK-N-MC) and those from cultured human leukemia cells (HL-60) separately, We transferred them onto the PVDF membranes, and then reacted them with anti-neuronal antibody-positive serum samples. By comparing the two panels and selected protein spots which were positive only in the panel of SK-N-MC as candidate for neuronal cell-specific autoantigens. We detected eleven protein spots and successfully identified five of them by MALDI-TOF/TOF mass spectrometry They are tubulin beta, heterogeneous nuclear ribonucleoprotein H, nucleophosmin, pyruvate dehydrogenase beta subunit and thioredoxin peroxidase 4. We are now promoting preparation of recombinant proteins for them to investigate the autoantibodies to them in larger numbers of patients together with further identification of the remaining candidate antigen spots.
