Fig. 1.

Loss of Cbl-b completely restores IgM-induced B cell proliferation in Cd40^−/− mice. A. Splenic B cells (2 × 10⁵/ml) from WT and Cd40^−/− BALB/c mice were stimulated for 72 h with different concentrations of F(ab’)₂anti-IgM mAb (left panel) or constant anti-IgM (2 μg/ml) with different concentrations of anti-CD40 mAb (0.2–8 μg/ml) (right panel). B cell proliferation was determined by [³H]-thymidine incorporation (meansSD). B. Splenic B cells (2 × 10⁶) from WT, Cd40^−/−, Cblb^–/– and Cblb^–/–Cd40^−/− mice were stimulated for 72 h with F(ab’)₂anti-IgM (2 μg/ml). B cell proliferation was determined. Data represent mean ± SD cpm for B cells from three individual mice. *p < 0.05; **p < 0.01; Student t-test.