Effect of Allele plus One A~tigey Match*

I t is now well established that compatibility for the t t L A antigens between donor and host siblings is generally associated with prolonged excellent function of renal allografts (1-6). Although it may not be possible to identify all of the possible antigens of both segregating series in transplant pairs, nonreactive mixed lymphocyte cultures (MLC) 1 have proven to be excellent predictors of HL-A compatibility and graft function. Controversy remains, however, as to what criteria of compatibility determined either by serologic typing (1 6) for HL-A antigens or degree of stimulation in MLC (1, 2, 7-13) can be relied upon to predict the next level of comparatively good transplant success. In this regard, Bach and others (2, 14-16) have stressed that within families donor-host compatibility for one allele is usually associated with intermediate stimulation in MLC as compared with two-allele compatibility or disparity. Seigler et al. (7), however, have noted rather remarkable overlap between the MLC responses between oneand two-allele mismatched cell donors. We have noted the same variability, but now report that a subgroup with low MLC stimulation may be distinguished bv the fact that the donor and host pair share one allele plus one antigen of the second unmatched allele as determined by lymphocytotoxicity testing for HL-A antigens.