(A) Mean PB WBCs, neutrophils, lymphocytes, and platelet (Plt) counts are shown in ex3op mice and nat mice at day +14 following 750 cGy TBI (n = 10/group). *P < 0.05, **P < 0.01, ***P < 0.001. ns, non-significant. (B) Mean BM cell counts, percentage of KSL cells, and numbers of KSL cells at day +14 following 750 cGy (n = 10/group). (C) Mean numbers of BM CFCs at day +14 (n = 10/group). ***P < 0.001. (D) The percentage survival of ex3op mice and nat mice is shown through day +30 following 750 cGy TBI (n = 12/group). *P = 0.03 by log-rank test for survival analysis. For all other analyses, 2-tailed Student’s t tests were performed. Data are presented as mean ± SEM.