FLOW-CYTOMETRY CROSS-MATCHING AND PRIMARY CADAVER KIDNEY GRAFT OUTCOME - RELEVANCE OF T-CELL AND B-CELL TARGETS, HISTORIC SERA AND AUTOLOGOUS CONTROLS

There is limited information regarding the role of flow cytometry cros smatching (FCXM) in primary cadaver kidney allografting and even less about B cell reactivity and graft survival (GS). Furthermore, there is little or no published data concerning reaction strength (cutoff valu e), the effect of historic sera reactions, and the usefulness of perfo rming autologous crossmatches (XMs) on GS. These factors were examined retrospectively on 214 primary transplants performed from August 1991 to January 1994 with follow-up to July 1995. Three-color FCXMs were d one on a 1024-channel BD-FACScan, and the shift in median channel fluo rescence (MCF) over the negative control was calculated. All patients had a negative T cell (AHG) and warm B cell (2 wash, extended incubati on) cytotoxicity XM, and none was excluded in calculating GS. A quanti tative effect was noted as stronger MCF shifts vs. T or B cells correl ated with decreased GS (r=0.98 and 0.92, respectively). Significant di fferences were seen with cutoff values of T=50 and B=110 which were 1. 7-1.8 times the SE above the mean MCF of normal sera controls. T neg p atients (n=198) had 1- and 3-yr actuarial GS of 86% and 79% compared t o T pos patients (n=16) of 75% and 49%, p=0.008. B neg patients (n=177 ) had 1- and 3-yr GS of 86% and 81% compared to B pos patients (n=37) of 78% and 47%, p=0.005. Most informative was the analysis of combined T and B cell FCXM results. Three year GS for T neg - B neg patients ( n=171) was 81%, and for T pos - B neg patients (n=6), it was 83%, p=0. 98. The 27 T neg - B pos group's GS was lower at 62% but did not reach significance. Poorest GS was seen for T pos - B pos patients (n=10) a t 23%, p=0.0001. Reaction patterns showed that T cells detected only H LA Class I antibodies, whereas B cells detected both Class I and II. H istoric sera (greater than or equal to 1 month old) reactivity influen ced GS. Patients with greater than or equal to 2 past sera positive bu t current serum negative reactions vs. T or T plus B cells (n=7) had a poor 29% GS, while those historically positive only vs. B cells (n=7) had 100% GS. On the other hand, patients positive only with the curre nt serum (n=16) had 2-yr GS of 100% (false positive test?), while pati ents whose current and historic sera reactions were positive (n=21) ha d a 25-50% GS (true positive test?). About 1 in 5 patients (19%) displ ayed positive autologous FCXM reactions. Subtraction of autologous MCF shift values from those vs. the donor converted 17 patients to the T neg - B neg or T pos - B neg group whose 2-yr actual GS was not signif icantly different (p>0.8) from those initially testing T neg B neg vs. their donors.