[Anti-NMDA receptor antibody in systemic lupus erythematosus]

N-Methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels with crucial roles in synaptic transmission and central nervous system plasticity. Systemic lupus erythematosus (SLE) is a multi-system inflammatory disorder characterized by the presence of autoantibodies directed against double-stranded (ds) DNA. The pathophysiology of neuropsychiatric (NP) SLE is diverse and complicated. In SLE, anti-dsDNA antibody (Ab) cross-reacts with NMDA receptors. Serum anti-NMDA receptor Ab was found in 30% of SLE patients. We demonstrated the relationship between anti-NMDA receptor Ab and each organ's involvement in SLE, and the biological function of anti-NMDA receptor Ab. The frequency of NP-SLE was significantly higher in the anti-NMDA receptor Ab positive subset than the negative subset, although the frequencies of serositis and nephritis were not significant. Anti-NMDA receptor Ab titer inversely correlated with leukocyte counts and hemoglobin levels. Moreover, regarding to the effects of anti-NMDA receptor Ab on NMDA receptor-transfected cell viability and intracellular Ca2+ level, there was a significant inverse correlation between anti-NMDA receptor Ab titer and cell viability, and a significant association between anti-NMDA receptor Ab titer and intracellular Ca2+ level. In conclusion, anti-NMDA receptor Ab is associated with NP-SLE and cytopenia. Anti-NMDA receptor Ab could cause the injury of NMDA receptor-expressed cells by increasing Ca2+ influx.