TGF‐β inhibits B cell proliferation, plasma cell differentiation, and antibody production, while IFN‐I, IL‐6, and TFH cells promote these processes.[31, 37] In agreement with the reduced levels of TGF‐β and increased levels of IL‐6, IFN‐I, and percentages of TFH cells in EBI2‐deficient cells or mice (Figure 7D,F and Figure S11F, Supporting Information), we found that Ebi2‐cKO lupus mice enhanced surface MHCII levels on B cells (Figure 7I) and increased the percentages of plasma cells (Figure 7J). The gene discussed is TGFB1; the disease is systemic lupus erythematosus.