Thymocytes and CD4⁺ T cells from pIV^−/− and I-Aα^−/− mice display a similar phenotype.

(A) Double-positive CD4⁺CD8⁺ thymocytes from pIV^−/− mice express higher levels of TCR and CD4 than controls (top 2 histograms). CD8 levels are similar to controls (data not shown). Single-positive CD4⁺ T cells display lower TCR levels in pIV^−/− and I-Aα^−/− thymuses compared to control littermates (middle 2 histograms). This is not observed for CD8⁺ T cells (bottom 2 histograms). (B) CD4⁺ splenocytes were analyzed by FACS for CD62L, CD54, and TCR expression. CD62L and TCR levels are lower in I-Aα^−/− and pIV^−/− CD4⁺ T cells than in controls. CD54 is increased in both mutants. (C) CD8⁺ T cells from the spleens of I-Aα^−/− , pIV^−/−, and control littermates are similar with respect to their expression levels of CD62L, CD54, and TCR.