Female recipient mice were killed at 2, 5, and 8 months after 0, 10, 50, 100 cGy. (A) Male marrow engraftment over time. (B) Southern blot showing 2-month time point. Kruskal-Wallis analysis and Cuzick two-sided test for trend over time showed that engraftment was sustained (eg, no downward trend) for bone marrow and spleen (not shown). Thymic engraftment (not shown) showed a modest decrease over time (P < .05 for all levels of irradiation).