Competitive repopulation assay between STAT5ab^−/− and wild-type FL grafts.

(A) C57Bl/6 FL cells (Hb_s and Ly-5.2) were obtained from embryonic day 14.5 fetuses from matings of STAT5ab^+/− or wild-type HW80 mice (Hb_d background). The STAT5ab^+/− cross FL cells were genotyped by PCR the same day, and then either wild-type or knockout cells were mixed with an equal donor equivalent of wild- type HW80 FL cells. The cells were transplanted into lethally irradiated adult C57Bl/6 recipient mice and analyzed 20 weeks later for the relative contribution of donor engraftment. A second experiment analyzed at 16 weeks is not shown. (B) For a third experiment, C57Bl/6 FL cells (Ly-5.2) were obtained as described above but were competed at either a 1:1 or a 4:1 ratio against wild-type Ly-5.1 FL cells. The cells were transplanted into lethally irradiated adult C57Bl/6 Ly-5.1 recipient mice and analyzed 10 weeks later for Ly-5.2 cells costaining for Gr-1, Mac-1, CD4, B220, or Ter119.