Fig. 2.

TCR expression in ATM-deficient mice. (a) (Top) Freshly explanted ATM WT (Left) and KO (Right) thymocytes were stained with anti-CD4, anti-CD8, and anti-TCRβ antibodies and gated to allow analysis of DP thymocytes. (Middle and Bottom) Anti-TCRβ staining was either cell-surface-specific or carried out after permeabilizing to measure total cellular TCRβ. The solid line indicates staining of ATM-deficient thymocytes, and the shaded area represents WT control thymocytes. The dotted line indicates staining of TCRβ-deficient thymocytes. (b–d) Thymocytes from ATM WT and KO mice were cultured for 4 h to allow the up-regulation of TCR expression and then stained with anti-CD4, anti-CD8, and anti-TCRβ antibodies and analyzed by flow cytometry. (b) Cell surface TCRβ expression is presented for the total number of thymocytes. The solid lines represent WT control thymocytes, and the dotted lines represent ATM KO thymocytes. (c) Thymocytes were gated to assess TCRβ expression on CD4⁺CD8⁺ DP thymocytes. ATM-deficient DP thymocytes have an increased proportion of TCR^lo and a decreased proportion of TCR^med cells. (d) TCRβ expression is equivalent on TCR^hi SP ATM KO and WT thymocytes. (e) Numbers of total DP cells, TCR^lo DP cells, and TCR^med DP cells in ATM KO and WT thymi.