p66Shc attenuates BCR signaling. (A left) Immunoblot analysis of Akt, Erk1/2, and Syk phosphorylation in postnuclear supernatants from the control and p66Shc-expressing Ramos B-cell transfectants activated with anti-IgM antibodies for the indicated times. (Right) Quantification by laser densitometry of the relative levels of Akt, Erk1/2, and Syk phosphorylation in control and p66Shc-expressing Ramos cells activated with anti-IgM antibodies. Data are expressed as the percentage of maximal activation in control cells (set as 100%; n = 3; ***P ≤ .001, **P ≤ .01, *P ≤ .05), where significance refers to the differences between p66Shc-expressing and control Ramos cells at each time point. (B top) Immunoblot analysis of Akt, Erk1/2, and Syk phosphorylation in postnuclear supernatants from splenocytes from wild-type and p66Shc^−/− mice activated with anti–mouse IgM antibodies for 2 minutes and 5 minutes (Syk), 5 minutes (Erk1/2), or 30 minutes (Akt). (Bottom) Quantification of the relative levels of Akt, Erk1/2, and Syk phosphorylation in splenocytes activated with anti-IgM antibodies (Syk, 2 minutes time point). Data are expressed as the percentage of maximal activation in splenocytes from wild-type mice (set as 100%; n > 3; ***P ≤ .001, **P ≤ .01, *P ≤ .05). Error bars indicate SD.