B6-derived Ly-5.2 cells exhibit competitive advantage in B6 recipients. (A top panel) Ly-5.2 cells increase significantly (#P < .0001) and Ly-5.1 cells decrease significantly (#P = .001) from 5 to 30 weeks after transplant in B6 recipients. Within the Ly-5⁺ population, the percentage of Ly-5.2 (mean ± SD) cells is significantly higher (*P = .001) than the percentage of Ly-5.1 (mean ± SD) cells at 30 weeks after transplant in B6 recipients. (Bottom panel) Ly-5.2 cells increase significantly (#P = .002) in B6.SJL recipients from 5 to 30 weeks after transplant. Within the Ly-5⁺ population, the percentage of Ly-5.1 cells (mean ± SD) is significantly higher (*P = .001) than the percentage of Ly-5.2 cells (mean ± SD) at 5 weeks after transplant in B6 recipients. (B) Within the Ly-5.1 population, the percentage of Mac-1/Gr-1 cells (mean ± SD) decreased significantly (##P = .009) in B6 and B6.SJL recipients, the percentage of B220 cells (mean ± SD) decreased significantly in B6 (#P = .03) but not B6.SJL (P = .5) recipients, and the percentage of Thy-1.2 cells dropped slightly (slope = −0.069) but not significantly (P = .6) in both strains. Cross-strain comparisons revealed a significant difference in Thy-1.2 cells at 5 (*P = .03) and 10 (*P = .02) weeks after transplant. Data were pooled from a total of 3 to 8 mice per strain at each time point.