Figure 4.

Trim21^–/– B cells proliferate more readily upon anti‐immunoglobulin (Ig)M stimulation. Spleen cells were cultured with either anti‐IgM, anti‐CD40 or without stimuli. Incorporation of thymidine was measured after 3 days. (a) anti‐IgM and (b) anti‐CD40 stimulation of total splenocytes from Trim21 ^+/+ and ^–/– (five per group). (c) Anti‐IgM stimulation of B cells purified from spleens (three per group). (d) Total splenocytes were cultured with 0·1 g/ml anti‐IgM for 4 days and expression of the proliferation marker Ki67 in CD19⁺ B cells was assessed by flow cytometry (six per group). (e) Activation‐induced cell death was assessed in anti‐IgM stimulated cells at day 5, 2 days after restimulation. Frequencies of live, annexin V⁺ apoptotic and annexin V⁺ 7‐aminoactinomycin D (7‐AAD)⁺ necrotic cells among Trim21 ^+/+ and ^–/– cells (six per group). Data are presented as mean ± standard error of the mean (s.e.m.). *P < 0·05 (Mann–Whitney I‐test)