Autoimmune features in p66Shc^−/− mice. (A) Autoantibody production in p66Shc^−/− mice. Sera from 12-month-old control (+/+) or p66Shc^−/− (−/−) mice were analyzed by ELISA for detection of anti-dsDNA antibody titers. Gray crosses show OD₄₅₀ for each mouse analyzed, while the black lines indicate the mean values (n ≥ 16). (B) p66Shc^−/− mice have increased levels of B1 cells in the peritoneal cavity. Peritoneal lymphoid cells were stained with anti-CD22/anti-CD5 fluorochrome-conjugated mAb. The bar graph shows the percentage ± SD of CD22⁺CD5⁺ cells in peritoneal lavages of control (gray) and p66Shc^−/− mice (black) (n ≥ 4; **P < .01). (C) Elevated serum IgG1 and IgG2a in p66Shc^−/− mice. Levels of IgG isotypes in the serum from 12-month-old wild-type (+/+) and p66Shc-deficient (−/−) mice were measured by ELISA. Gray crosses show IgG concentration (mg/mL) for each mouse analyzed, while the black lines indicated the mean values (n ≥ 20).