Single‐cell RNA sequencing reveals diverse B cell phenotypes in patients with anti‐NMDAR encephalitis

Abstract

BackgroundsAnti‐N‐methyl‐D‐aspartate receptor encephalitis (NMDAR‐E) is a severe autoimmune disorder characterized by prominent psychiatric symptoms. Although the role of NMDAR antibodies in the disease has been extensively studied, the phenotype of B cell subsets is still not fully understood.MethodsWe utilized single‐cell RNA sequencing, single‐cell B cell receptor sequencing (scBCR‐seq), bulk BCR sequencing, flow cytometry, and enzyme‐linked immunosorbent assay to analyze samples from both NMDAR‐E patients and control individuals.ResultsThe cerebrospinal fluid (CSF) of NMDAR‐E patients showed significantly increased B cell counts, predominantly memory B (Bm) cells. CSF Bm cells in NMDAR‐E patients exhibited upregulated expression of differential expression genes (DEGs) associated with immune regulatory function (TNFRSF13B and ITGB1), whereas peripheral B cells upregulated DEGs related to antigen presentation. Additionally, NMDAR‐E patients displayed higher levels of IgD−CD27− double negative (DN) cells and DN3 cells in peripheral blood (PB). In vitro, DN1 cell subsets from NMDAR‐E patients differentiated into DN2 and DN3 cells, while CD27+ and/or IgD+B cells (non‐DN) differentiated into antibody‐secreting cells (ASCs) and DN cells. NR1‐IgG antibodies were found in B cell culture supernatants from patients. Differential expression of B cell IGHV genes in CSF and PB of NMDAR‐E patients suggests potential antigen class switching.ConclusionB cell subpopulations in the CSF and PB of NMDAR‐E patients exhibit distinct compositions and transcriptomic features. In vitro, non‐DN cells from NMDAR‐E can differentiate into DN cells and ASCs, potentially producing NR1‐IgG antibodies. Further research is necessary to investigate the potential contribution of DN cell subpopulations to NR1‐IgG antibody production.