Repression of T-lymphoid genes in Pax5-expressing thymocytes. (A) RT-PCR analysis of the indicated genes in sorted pro-B cells from wild-type (wt) bone marrow and in sorted DP thymocytes from wild-type, IgH^P5ki/P5ki, and Ik^Pax5/+ mice. The cDNA was normalized for equal expression of the hypoxanthine phosphoribosyltransferase (Hprt) gene prior to semiquantitative PCR of 5-fold serial cDNA dilutions. (B) CD28 and CD11a (Itgal) expression on gated DP thymocytes of Ik^Pax5/+ and control Ik^neo/+ mice (filled areas) as compared with wild-type DP thymocytes (black lines). The mean fluorescence is indicated by vertical dashed lines.