Human Brain Protein Antigens Reacting with Autoantibodies from Systemic Lupus Erythematosus Patients with Central Nervous System Manifestation

Abstract

Autoantibodies to neuronal cell antigen have been proposed to be responsible for central nervous system (CNS) disease in patients with systemic lupus erythematosus (SLE). However, the target antigen molecules in human brain tissue responsible for the development of CNS dysfunction in SLE patients have not yet been identified. To identify the specific human brain proteins associated with CNS dysfunction in SLE, we measured the autoantibodies to both human brain proteins and extractable nudear antigen from calf thymus by ELISA, and characterized the human brain autoantigen by immunoblot analysis using sera from 15 SLE patients with diffuse CNS manifestation, 14 SLE patients without CNS manifestation, and 16 healthy subjects as controls. Although the levels of autoantibodies to both human brain proteins and extractable nudear antigen were higher in SLE patients than the controls (p< 0.05), there were no significant differences in the levels between SLE patients with or without CNS manifestation (p> 0.05). On immunoblot analysis, autoantibodies to 38 kDa protein in human brain tissue were positive in 6 (86%) of 7 SLE patients with CNS manifestation, 2 (29%) of 7 SLE patients without CNS manifestation, and one (20%) of 5 controls, and a significant difference in positive rates was noted between two SLE groups (Chi-square test; p< 0.05). In conclusion, the 38 kDa human brain protein may be an important target for autoantibodies in sera of SLE patients with CNS manifestation, and further study is essential to confirm the pathogenic significance of this autoantigen.