Thymocytes deleted for Hdac1/2 fail to undergo positive selection. Experiments were performed on thymocytes isolated from mice at 3-4 weeks of age. (A) FACS analysis of TCRβ expression levels in mice of the indicated genotype. (B) Two-color FACS analysis on thymocytes isolated from mice of the indicated genotype (n > 6). (C) Percentage and cellularity (mean ± SEM n = 4) of wild-type and Hdac1^Δ2/Δ2; Hdac2^Δ2/WT thymocytes in the presence of an OTII-TCR transgene. (D) Cellularity of single positive (SP) thymocytes, total, CD4SP and CD8SP mean ± SEM are shown. (n = 4 for all genotypes).