Regulator of G protein signaling (RGS) proteins inhibit chemokine signaling by desensitizing G protein–coupled receptor signals. This study was undertaken to determine the mechanisms by which RGS13 promotes the generation of pathogenic autoantibodies in germinal centers (GCs), using BXD2‐Rgs13^−/− mice.

Confocal and light microscopy imaging techniques were used to determine the location of cells that express RGS13 and activation‐induced cytidine deaminase (AID) in the mouse spleen, and the number of plasmablasts. The levels of GC and plasma cell program transcripts in GC B cells were determined by real‐time quantitative polymerase chain reaction (qPCR). Differential interleukin‐17 (IL‐17)–mediated expression of RGS13 in GC versus non‐GC B cells was analyzed using A20 and 70Z/3 B cells.

In the spleens of BXD2 mice, RGS13 was mainly expressed by GC B cells and was stimulated by IL‐17 but not IL‐21. IL‐17 up‐regulated RGS13 in A20 GC cells but not 70Z/3 non‐GC B cells. BXD2‐ Rgs13^−/− mice exhibited smaller GCs and lower AID levels, suggesting lower somatic hypermutation and affinity maturation. However, GC B cells from BXD2‐ Rgs13^−/− mice showed increased levels of IgM^bright plasmablasts, up‐regulation of the genes encoding plasma program, including interferon regulatory factor 4, B lymphocyte–induced maturation protein 1, and X‐box binding protein 1 and the p‐CREB target genes Fosb and Obf1, and down‐regulation of the GC program genes Aid, Pax5, and Bach2 compared to BXD2 mice. BXD2‐Rgs13^−/− mice had lower titers of IgG autoantibodies and IgG deposits in the glomeruli, suggesting reduced autoantibody pathogenicity.

RGS13 deficiency is associated with a reduction in GC program genes and the exit of fewer pathogenic IgM plasmablasts in BXD2 mice. Our findings indicate that prolonged GC program, mediated by up‐regulation of RGS13, enhances AID expression and enables the generation of pathogenic autoantibodies in autoreactive GCs.