Comparison of engraftment with HW80 background BM cells following injection into either irradiated or nonirradiated hosts. (A) To determine engraftment levels of STAT5ab^–/– or wild-type HW80 BM cells into irradiated hosts, mice were given transplants and peripheral red blood cells were analyzed by hemoglobin electrophoresis for the Hb_d contribution 12 weeks following injection. This was compared with injection of the same donor BM cells into W/W^v hosts, in the absence of any myeloablative conditioning. Each lane on the hemoglobin gels represents a single mouse. (B) Summary of the engraftment efficiency for HW80 and C57BL/6 mice of either the wild-type or STAT5ab^–/– genotype. ▪ represents the total number of injected W/W^v mice, and □ the number of those injected that actually showed engraftment by hemoglobin electrophoresis.