Consequences of hTAL-1 expression on thymus cellularity.

(A) hTAL-1 protein expression in the thymus. Paraffin-embedded thymus sections were stained with the BTL-73 monoclonal antibody that recognizes the hTAL-1 protein but not the mTAL-1 protein (original magnification, × 120). (B) Photo showing a representative wild-type (Wt) and transgenic (Tg) thymus of two 4-week-old sex-matched littermates. (C) Analysis of T-cell subsets. Thymocytes freshly isolated from sex-matched wild-type, L6, and Δb L3 littermates at 12 weeks after birth were stained with anti-CD4–FITC and anti-CD8–PE antibodies. The percentages of marked cells are indicated in the quadrants. A representative experiment of 6 is shown. Original magnification × 5. (D) Level of TAL-1 protein in Jurkat and L6 thymocytes. Total protein extracts (50 μg) of Jurkat and L6 thymocytes were subjected to Western blot using the human TAL-1–specific antibody BTL-73 monoclonal antibody. Quantification of hTAL-1 protein, after normalization by Coomassie blue staining, showed that the hTAL-1 protein level in Jurkat was at least 4 times higher than in L6 transgenic thymocytes.