Reported HLA relationships in cases of TA-GVHD. (A) Donor-recipient relationships for HLA class I and class II in cases of TA-GVHD. D = 0 indicates an absence of donor antigens foreign to the recipient. D ≥ 1 indicates the presence of ≥1 foreign donor antigens. Shaded areas indicate cases in which an absence of foreign donor antigens was reported at either HLA class I or class II loci. (B) Among those in whom the presence or absence of D = 0 could be definitively determined, donor stealth (D = 0) was present in 55 of 57 (96%) of those without an indication for irradiation. In contrast, donor disparity (D ≥ 1) was present in 58% (7 of 12) of patients with an indication for blood irradiation. (P < .0001).