26-P

Abstract

Aim A positive crossmatch is considered a contraindication for kidney transplantation. Interestingly, we have observed a high rate of positive T-cell FCXM results in the absence of donor-specific antibodies (DSA) in patients infected with human immunodeficiency virus (HIV). This study was aimed to determine the cause of these aberrant results. Methods Twenty-six HIV+ patients were tested by T- and B-cell FCXM. A total of 348 sera were tested with pronase-treated (PT) cells, and 81 sera were tested with pronase-nontreated (NT) cells from 196 different deceased donors. Selected 0% PRA sera (n=4) were tested with purified PT and NT CD4+ and CD8+ T-cells. Also, selected 0% PRA sera (n=4) were pre-treated with various reducing agents (DTT, 2-ME or TCEP) and with Adsorb Out™ beads (One Lambda) and then tested with PT cells. Positive T- and B-cell FCXM represented MCS values of >20 and >30, respectively. Results The majority of the patients (97.1%) exhibited a positive T-cell FCXM with PT cells (MCS = 62.0 ± 22.8) in the absence of DSA; only 17.2% had the same result with NT cells (MCS = 9.6 ± 13.7) (p Conclusions Pronase treatment induces false-positive T-cell FCXM results in HIV+ patients. These results are not due to non-specific antibody binding because it is not observed on B-cells and reducing agents have no effect on the results. Laboratories using pronase in their FCXM protocol should consider testing HIV+ patients with both PT and NT cells to prevent these patients from being inappropriately excluded from receiving an organ due to false-positive FCXM results.