CORRELATION OF RELATIVE RESPONSE INDEX WITH MARROW GRAFT REJECTION IN PATIENTS WITH APLASTIC-ANEMIA

Patients (34) with severe aplastic anemia were treated with cyclophosphamide or total body irradiation and an infusion of marrow from a genotypically HL-A-identical sibling donor. Engraftment occurred in all patients, but rejection was noted in 12. Mixed leukocyte culture (MLC) test undertaken before grafting to determine donor-recipient histocompatibility were analyzed retrospectively. The response of patients cells to sibling cells in mixed culture was compared to the response of patient cells to cells of an unrelated individual and expressed as a relative response index (RRI). Of the 12 patients who showed positive RRI to donor leukocytes in pregraft MLCs, 9 rejected their grafts, whereas of 23 patients with negative RRI only 3 rejected their grafts (P < 0.005). The MLC test can apparently detect individuals who are most likely to reject their HL-A identical sibling graft.