HYPERACUTE RENAL-ALLOGRAFT REJECTION FROM ANTI-HLA CLASS-1 ANTIBODY TO B-CELLS - ANTIBODY DETECTION BY 2 COLOR FCXM WAS POSSIBLE ONLY AFTERUSING PRONASE-DIGESTED DONOR LYMPHOCYTES

We present a report of a transplant recipient who lost her renal allog raft from hyperacute rejection. This was secondary to a weak IgG anti- HLA class I antibody that was only reactive to donor B lymphocytes. Th is antibody was not detected in her pretransplant serum by the convent ional complement-dependent cytotoxicity assays using donor blood lymph ocytes. Pretransplant sera were analyzed retrospectively by two-color flow cytometric crossmatching (FCXM). It was difficult to determine if the recipient's serum contained an IgG antibody specific for HLA on d onor B cells since IgG from control AB sera and pretransplant sera bou nd equally well to CD19 B cells. However, when donor lymphocytes were pretreated with pronase to digest the membrane receptor for Fc domain of IgG (Fc gamma R) on non-T-cells, control IgG in AB serum did not bi nd to B cells and, hence, it was easy to detect binding of IgG (in pre transplant sera) to HLA on B cells. This case underscores the importan ce of identifying weak anti-HLA class I antibodies reactive only to B cells. Moreover, it shows that the currently used two-color FCXM lacks the specificity to detect such antibodies.