IDENTIFICATION OF PATIENTS AT RISK FOR INFERIOR RENAL-ALLOGRAFT OUTCOME BY A STRONGLY POSITIVE B-CELL FLOW-CYTOMETRY CROSS-MATCH

To evaluate the influence of a positive B cell flow cytometry crossmat ch (FCXM) on transplant outcome, we retrospectively performed B cell F CXMs for 431 consecutive cadaver renal transplant recipients using the two most current pretransplant sera. All transplant recipients had a negative lymphocytotoxic antiglobulin T cell XM and a negative (less-t han-or-equal-to 10 channel shift) T cell FCXM. B cel FCXMs were perfor med using a two-color technique to identify binding of IgG antibody to donor lymph node B lymphocytes stained for CD20. The incidence and ca uses of graft failure posttransplant were determined by requesting thi s information from recipient transplant centers. Transplants that fail ed due to nonimmunological causes (n=54, 13%) were excluded from the a nalysis. Minimum follow-up was 12 months. We found no difference in gr aft survival at one year for transplants where the B cell FCXM was pos itive in the range of 11 to 50 channel shift (n=201) compared with tho se with a negative (less-than-or-equal-to 10 channel shift) B cell FCX M (n=141)-i.e., 90% vs. 91%, P=NS. However, when the positivity in the B cell FCXM was >50 channel shift (n=35), significantly fewer grafts survived at one year, compared with those where the channel shift was less-than-or-equal-to 50 (n=342),63% vs. 91%, P<0.001. This was true f or first transplants as well as regrafts and for transplants performed with a positive as well as a negative standard B cell XM. The detrime ntal effect of a positive B cell FCXM was seen for sensitized (PRA >10 % at the time of transplant) as well as nonsensitized patients. Howeve r, this effect was observed only when the donor had at least a one-DR mismatch. We conclude that a strongly positive B cell flow cytometry c rossmatch identifies patients who are at risk for graft loss. Since th e risk appears to be only when there is a DR mismatch, the data sugges t that the B cell-specific IgG antibody detected by flow cytometry may be specific for the mismatched MHC class II antigens of the donor.