Figure 1.

BCR-induced protein tyrosine phosphorylation in B cells from CD22-deficient mice (CD22^−/−) and wild-type littermates. Purified splenic B cells were incubated with either medium or anti-IgM antibodies (40 μg/ml) at 37°C. Cells (10⁷) were removed from the cultures at the indicated times and solubilized. Cell lysates (40 μg/lane) were subjected to SDS/PAGE and transferred electrophoretically to a membrane for subsequent anti-phosphotyrosine immunoblotting. Molecular weight standards (×10⁻³) are shown on the right. Arrows indicate major bands that were different between CD22-deficient and wild-type B cells. Results are representative of those obtained with three littermate pairs of mice.