Evaluation of the concordance between GluN1-GluN2 heteromer live-cell-based assay and GluN1 monomer biochip kit assay on anti-NMDAR autoantibody detection.

Anti-N-methyl-d-aspartate receptor (NMDAR) antibodies are most frequently detected in autoantibody-related autoimmune encephalitis. Anti-NMDAR encephalitis mainly affects young women with ovarian teratoma, including acute to subacute onset of psychosis, seizures, consciousness disturbance, dyskinetic involuntary movements, autonomic dysfunction, and others. Diagnosis is based on the detection of anti-NMDAR autoantibodies in cerebrospinal fluid (CSF). The autoantibody recognizes the conformational epitope of the NMDA receptor. NMDA receptors contain hetero-tetramers of GluN1 (NR1) and GluN2/3 (NR2/3), in which GluN1 is essential to form functional receptors on the synaptic membrane in the brain. Thus, the autoantibodies are detected using neurons or culture cells expressing conformational receptors on their cell membrane, the natural form in the brain. The antibodies detected using artificial GluN1 monosubunit expressing cells as the antigens have been widely used for anti-NMDAR-antibody test. In the present study two detection systems were compared, a live-cell-based assay using human embryonic kidney (HEK) 293 cells expressing both of GluN1 and GluN2B, and a commercially available GluN1-monotransfected HEK cell biochip system. As the result, both the methods were equivalent, and the clinical features of both groups were similar, suggesting both tests have equal clinical significance.