Protein kinase Cβ (PKCβ) deficiency impairs the B cell receptor response and survival of B cells from Sle mice. A, In vitro responses of B cells to anti-IgM or lipopolysaccharide (LPS) stimulation. Splenocytes from 6-month-old mice were labeled with 5,6-carboxyfluorescein succinimidyl ester (CFSE) (shaded area) and stimulated with anti-IgM or LPS or were left in the medium without any added stimuli for 48 hours (black lines). Top, PKCβ deletion reduced the proliferative response of B cells to anti-IgM stimulation but not LPS stimulation. Bottom, PKCβ deficiency reduced up-regulation of CD69 and CD86 expression, as determined by fluorescence-activated cell sorting analysis. B, Effect of PKCβ deficiency on cell viability. Purified spleen B cells from the indicated mouse strains were incubated in RPMI 1640 medium. Cell viability was assayed by flow cytometry, using an annexin V detection kit. Bars show the mean ± SD. C, Expression of Bcl-xL in anti-IgM–stimulated splenocytes from the indicated mouse strains, as analyzed by Western blotting. Actin was used as a loading control. D, Effect of PKCβ deletion on calcium signaling in B cells from Sle mice. Splenocytes from the indicated mouse strains were loaded with 1 μM Fura Red to evaluate their ability to flux Ca2+ in response to anti-IgM. B220+ cells were gated for the analysis. All data shown are representative of at least 2 independent experiments.