Reduced proliferation and activation of toll-like receptor 9 (TLR9)-stimulated B cells from systemic lupus erythematosus (SLE) patients compared to healthy donors. (A) Representative flow cytometry plots showing the gating strategy and histograms of the frequency of proliferating B cells and induction of CD38 expression after 2 days of peripheral blood mononuclear cells (PBMC) culture with or without CpG stimulation. (B) Combined data from 6 SLE patients and 10 healthy donors for the frequency of proliferating (Ki-67+) B cells (left graph) and the induction of CD38 expression by B cells (right graph). (Mann-Whitney U-test; ns, not significant *P <0.05). HD, healthy donors.