Transplantation of α4^- (Δ/Δ) BM or α4^- (Δ/Δ) PB cells in lethally irradiated recipients. (A) Transplantation outcomes of mice given α4^Δ/Δ BM donor cells killed at 10 or 56 weeks after transplantation (Table 1). Secondary transplantations (Table 3) were done at 10 or 56 weeks after primary transplantation and were tested 16 and 26 weeks after secondary transplantation (white mice, < 10% α4⁺ cells; gray mice, > 10% α4⁺ cells; black mice, dead). Note the tendency in all secondary transplant recipients for reconstitution by surviving α4⁺ cells from hosts (gray mice). In tertiary transplants, there was only 30% survival (B), and the 6 surviving mice (no. 1-6 in Figure 5C) were reconstituted mostly (mice no. 1-4) by host cells that were neo-negative (= WT). Two mice (no. 5, 6) showing neo⁺ in panel C were not reconstituted by unablated α4^f/f cells, but by host cells, since these recipients were f/f/cre(-)/neo⁺ mice.