Inhibition of GVHD by granulocytes requires activation and histocompatibility. Irradiated (C57BL/6 × BALB/c) F1 receptors mice received BMTD and T cells from C57BL/6 mice plus LDGs from C57BL/6 mice (A), allogeneic third-party LDGs from A/J mice (B), or non–G-CSF–treated HDGs from C57BL/6 mice (C). After 22 days the animals were killed and the intestines were submitted to histopathologic analysis. Intense inflammatory foci in lamina propria is observed in A/J LDGs (B) and HDGs recipient (C) with mononuclear cells (B, inset) and mixed inflammatory infiltrate (^*C, inset) associated with crypt cell apoptosis (arrows). Original magnifications, 40 × (A-C); 400 × (B, inset); 1000 × (C, inset). Results are representative of 1 of 5 experiments.