Analysis of engraftment and survival of Ly-5.1 hosts from experiment 1 receiving tertiary transplants of wild-type and STAT5ab^-/- BM cells. (A) BM cells that were harvested from 2 Ly-5.2 wild-type and 2 STAT5ab^-/- mice were serially transplanted into lethally irradiated Ly-5.1 recipients. Some of the mice that received secondary transplants were killed, and the BM was injected into lethally irradiated Ly-5.1 tertiary hosts. The mice were bled 30 weeks following tertiary transplantation, and the peripheral blood leukocytes were analyzed by FACS for the expression of Ly-5.2 or Ly-5.1. The percentage of donor Ly-5.2⁺ cells for representative recipients of wild-type (WT) or STAT5ab^-/- BM cells is shown on the x-axis. Gates were defined on the basis of the forward and side scatter characteristics for total viable nucleated cells. (B) Because the engraftment levels were low in tertiary recipients of STAT5ab^-/- BM cells, the BM cells from the remaining mice that received secondary transplants were collected and sorted for Ly-5.2⁺ cells. These cells were then injected into lethally irradiated Ly-5.1 hosts, and survival of recipient mice was determined by monitoring mice daily. Shown are the percentages of the total number of mice surviving (y-axis) at the particular time following tertiary transplantation (x-axis).