Figure 1.

The bcl-2 transgene (Eμ-bcl-2-25) is functional in T cell progenitors in c-kit and γ_c mutant thymocytes. Nontransgenic (open symbols) or Eμ-bcl-2-25 transgenic (filled symbols) total thymocytes from 5-d-old c-kit⁺γ_c ⁺ (A) or c-kit⁺γ_c ⁻ mice (B), or c-kit⁻γ_c ⁺ mice (C), or cell sorter–purified progenitor subsets (CD3⁻CD4⁻CD8⁻ [TN]) c-kit⁺CD25^-CD44⁺ (TN 1) (D), or c-kit⁺CD25⁺CD44⁺ (TN 2) (E) from 5-d-old c-kit⁺γ_c ⁺ mice were compared for their survival capacity ex vivo. Each symbol represents an individual mouse for each genotype. Thymocytes were placed in normal cell culture medium in vitro, and, at indicated times after initiation of the culture, numbers of viable cells were determined. The Eμ-bcl-2-25 transgene is functional in all of these growth factor receptor mutants, and, importantly, promotes thymocyte survival at those stages, in which mutations in c-kit or γ_c impair thymocyte development (TN 1 and TN 2). Due to the complete absence of thymocytes in the combined absence of c-kit and γ_c, the corresponding analysis could not be performed on c-kit⁻γ_c ⁻ mice.