Figure 5.

Expression of Blk(Y495F) protein at sequential stages of lymphoid development. Bone marrow cells were obtained from macroscopically tumor-free Blk(Y495F)-15 transgenic mice (lanes 1–3) or nontransgenic littermates (lanes 4–6) at 4–6 weeks of age. B220⁺CD43⁺ (lanes 3 and 6) and B220⁺CD43⁻ (lanes 2 and 5) populations were purified by FACS. Protein corresponding to 10⁵ cells from unfractionated bone marrow (lanes 1 and 4) or sorted populations was assayed for Blk by immunoblotting. Thymocytes were prepared from macroscopically tumor-free Blk(Y495F)-6 (lanes 7–10) or Blk(Y495F)-13 (lanes 11–14) transgenic mice at 4–6 weeks of age. CD4⁻CD8⁻ (lanes 8 and 12), CD4⁺CD8⁺ (lanes 9 and 13), and CD4⁺CD8⁻ (lanes 10 and 14) populations were purified by FACS. Protein corresponding to 10⁶ cells from unfractionated thymus (lanes 7 and 11) or sorted populations was assayed for Blk by immunoblotting. The apparent sizes (in kDa) and positions of molecular mass standards are indicated.