Two patterns of sensitization demonstrated by recipients of donor-specific transfusion. Limitations to control by Imuran.

Characteristics of the sensitization response to donor-specific transfusion (DST) have been studied in the context of the pretransfusion panel reactive antibody (PRA) status of the recipient. Two distinct patterns of response to DST and Imuran treatment have been found. In patients with one-haplotype-matched donors, the panel nonreactive patient (PRA less than 10%) has a 19% incidence of DST sensitization that is further reduced by Imuran treatment to 6%; antibodies are both anti-T cell and anti-B cells, are transient, and are specific to the mismatched HLA antigens of the blood donor. Panel-reactive patients (PRA greater than 10%) have a 56% incidence of DST sensitization; the antibodies appear within 2 weeks of the first transfusion, are anti-T cell, and are generally of broad specificity and persistent duration consistent with amplification of a previous antigenic exposure; Imuran seems to have little or no effect in reducing the incidence of sensitization in these panel-reactive patients. However, panel reactive patients whose PRA levels spontaneously fall to panel-nonreactive levels immediately prior to DST therapy have an exceedingly low (0-8%) incidence of sensitization with or without Imuran coverage.