B CELL CROSSMATCHING AND KIDNEY ALLOGRAFT OUTCOME IN 9031 UNITED
STATES TRANSPLANT RECIPIENTS.
RJ MAHONEY, S TARANTO, E EDWARDS, NORDX, PORTLAND, ME, UNOS, RICHMOND, VA.
The predictive power of a positive B cell crossmatch remains controversial in kidney transplantion. In this national study, one of the largest to date, we investigated whether T cell-neg, B cell-pos crossmatch kidney grafts experience rejection reactions and graft survival rates at 1, 3, 6 and 12 mos post Tx that are comparable to T cell-neg, B cell-neg crossmatch transplants.
UNOS OPTN/Scientific Registry data were analyzed on 15,896 cadaveric kidney graft recipients during 1994-1995 for graft outcome of 336 T cell-neg, B cell-pos transplants vs. 8695 T cell-neg, B cell-neg grafts. Data analyzed included donor-recipient demographics, sensitization levels, B cell crossmatch techniques used, histocompatibility mismatching, graft rejection incidence, early graft loss, cause of graft failure and statistical analyses (univariate and multivariate) in primary and repeat graft recipients.
Fifty-seven percent of the 15,896 transplant recipients (n=9031) were B cell crossmatched, and 336 of these 9031 recipients (3.7%) were transplanted with a B cell-pos crossmatch (T cell-neg). Sixteen percent experienced early graft loss (<6 mos) compared to 11% of B cell-neg grafts p<0.001. Lower graft survival rates at 1, 3. 6 and 12 mos post Tx (primary and regrafts) were observed in the B cell-pos vs B cell-neg patient groups, and these outcomes were statistically significant at each time point (two-sample t test, p<0.001). There was a 68% increase in the odds of 3 month graft loss in B cell-pos vs. B cell-neg recipients (multivariate logistic regression analysis P=0.054, 95% confidence interval 0.99-2.85). Demographic factors that were statistically significant included histocompatibility mismatching at HLA-A, HLA-A plus B and HLA-DR loci, pretransplant transfusions, peak and most recent PRA levels, a previous kidney graft, urine in first 24 hrs and rejection incidence between discharge and 6 mos post Tx.
In conclusion, positive B cell crossmatch primary and repeat grafts experienced an increase in graft rejection incidence (p <0.023) and early graft loss (p<0.001). Thus, a positive B cell crossmatch is predictive of inferior kidney graft outcome. The incidence of early graft loss and graft rejection may be reduced if transplant candidates demonstrating pretransplant antibody to donor B cells are temporarily denied a graft until T and B cell negative crossmatch donors are identified.