Functional defects of DPWY mb1 B cells. Representative proliferation plots for live B220⁺ bone marrow B cells stimulated for 72 hours with (A) LPS, (B) anti-CD40 monoclonal antibody, and (C) summary data of the division index of bone marrow B220⁺ B cells stimulated for 72 hours with the indicated stimuli. Data shown are representative of n = 8 LMC and n = 8 mb1^DPWY mice from 4 independent repeats for LPS, anti-IgM, and PI and n = 5 LMC and n = 3 mb1^DPWY from 2 independent repeats for anti-CD40. Data are shown as the mean ± SEM. (D) Endogenous levels of serum IgG, IgM, IgA, and IgG2c were measured by ELISA as described in the “Methods.” Data shown are for n = 28 LMC mice, n = 14 mb1^Traf3−/−, n = 12 mb1^DPWY, and n = 5 CD21^DPWY mice. Data are presented as mean ± SEM. (E) Serum levels of anti-dsDNA antibodies were measured at 3 months of age, data are shown as the mean ± SEM for n = 5 LMC, n = 10 alternative pathway, n = 9 mb1^DPWY, and n = 8 CD21^DPWY mice. *P < .05, ***P < .001.