Preconditioning injury or host immune function does not contribute to impaired GVHD sensitivity in asmase^−/− recipients. (A) Wild-type and asmase^−/− C57BL/6 mice were exposed to 11-Gy split-dose radiation (5.5 Gy × 2 separated by 3 hours) or 11-Gy single dose. Proximal jejunum was harvested 3.5 days thereafter, and the microcolony assay performed according to the method of Withers and Elkind.³⁵  Data (mean ± SEM) were compiled from 2 to 4 animals irradiated concomitantly, with 10 to 20 circumferences scored per mouse. (B) Irradiated (350 cGy split-dose) SCID-C57BL/6^asmase+/+ or SCID-C57BL/6^{asmase−/−} mice received BM and T cells as in Figure 1A, and were monitored for survival. Note that SCID-C57BL/6^{asmase−/−} mice died with significant lung and central nervous system damage consistent with development of accelerated NPD while displaying only minimal to moderate evidence of GVHD (supplemental Table 2). (C) Actuarial survival of 8- to 12-week-old male wild-type and asmase^−/− C57BL/6 mice exposed to 10 or 12 Gy whole-body radiation. Actuarial survival was calculated by the product-limit Kaplan-Meier method. Nine to 12 animals were irradiated per group.