Analysis of in vivo lymphocyte functions of cd28−/−scurfy mice. Serum from cd28−/− and cd28+/+scurfy mice were analyzed for (A) interleukin-4 and interferon-γ, and (B) immunoglobulin isotypes. WT: C57BL/6, 28(-): cd28−/− mice with C57BL/6 background, 28(-) sf: cd28−/−scurfy mice, sf: cd28+/+scurfy mice (mean ± SD, n = 3).