ABO and graft versus host disease: The frequency of donor group antigens on vessel endothelium ranged widely from 0.1 to 17.5% in these patients with pulmonary GVHD but no endothelial ABO chimerism was observed in the 3 samples from patients unaffected by GVHD (9.28% ± 6.59 vs. 0 ± 0, p < 0.001).