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Clinical and pathogenic significance of IgG, IgA, and IgM antibodies against the NMDA receptor

2018; Lippincott Williams & Wilkins; Volume: 90; Issue: 16 Linguagem: Inglês

10.1212/wnl.0000000000005329

1526-632X

Makoto Hara, Eugenia Martínez‐Hernández, Helena Ariño, Thaís Armangué, Marianna Spatola, Mar Petit‐Pedrol, Albert Saiz, Myrna R. Rosenfeld, Francesc Graus, Josep Dalmau,

Cellular transport and secretion

Objective To determine the frequency and clinical relevance of immunoglobulin (Ig)G, IgA, and IgM N -methyl-d-aspartate receptor (NMDAR) antibodies in several diseases, and whether the IgG antibodies occur in disorders other than anti-NMDAR encephalitis. Methods Evaluation of IgG, IgA, and IgM NMDAR antibodies in serum of 300 patients with anti-NMDAR encephalitis, stroke, dementia, schizophrenia, or seronegative autoimmune encephalitis. Antibodies and their effect on cultured neurons were examined with cell-based assays and brain and live neuronal immunostaining. Retrospective analysis of the clinical diagnoses of a cohort of 1,147 patients with IgG NMDAR antibodies identified since 2005. Results Among the 300 patients studied, IgG NMDAR antibodies were only identified in those with anti-NMDAR encephalitis and all reacted with brain and live neurons. By cell-based assay, IgA or IgM antibodies were detected in 22 of 300 patients (7%) with different diseases, but only 10 (3%) reacted with brain and 7 (2%) with live neurons. In cultured neurons, IgG but not IgA or IgM antibodies caused a decrease of synaptic and extrasynaptic NMDAR. Among the cohort of 1,147 patients with IgG NMDAR antibodies, 1,015 (88.5%) had anti-NMDAR encephalitis, 45 (3.9%) a limited form of the disease, 41 (3.6%) autoimmune post–herpes simplex encephalitis, 37 (3.2%) overlapping syndromes (anti-NMDAR encephalitis and demyelinating disease), and 9 (0.8%) atypical encephalitic syndromes; none had schizophrenia. Conclusions IgG NMDAR antibodies are highly specific for anti-NMDAR encephalitis and cause a decrease of the levels of NMDAR. In contrast, IgA or IgM antibodies occur infrequently and nonspecifically in other diseases and do not alter the receptor levels.