The effect of mismatching for HLA-DR in recipients of renal allografts sharing one HLA-ABC haplotype with related donors.

The effects of mismatching for DR antigens on renal allograft survival rates have largely been restricted to analyses of cadaver transplant results. Analyses of HLA matching in recipients of transplants from related donors have focused on the number of haplotypes shared between the recipients without regard to DR, or on the total number of HLA antigens mismatched, or on the degree of MLC responsiveness of the recipient to the donor. Most related donor-recipient pairs sharing only one HLA haplotype will be mismatched for DR at the other haplotype, but because there are a limited number of DR alleles, sharing of DR antigens on the mismatched haplotypes occurs relatively frequently. To determine the influence of mismatching for DR on the fate of renal allografts from related donors, we analyzed the results of 172 kidney transplants from related donors who shared one HLA-ABC haplotype with the recipient. There were 156 primary grafts and 16 retransplants; 147 donor-recipient pairs were satisfactory typed for DR antigens. Because genotyping was not usually done, we performed two analyses under two different assumptions. The first assumption was that individuals expressing less than or equal to 1 DR antigen had null antigens, or were homozygous for DR; the alternative assumption was that blanks were true antigens and individuals with blanks were heterozygous. The first assumption is more likely to be correct, and is the assumption used in most analyses of the effect of DR antigen mismatches on the results of cadaveric transplantation. Under the first assumption, of the 147 related donor-recipient pairs in whom DR typing was satisfactory, 33% were mismatched for 0, 64% for 1, and 3% for 2 DR antigens. The one-year absolute graft survival rates in recipients of kidneys from donors with 0 mismatches for DR was 92% (n = 49); in those with one mismatch for DR it was 82% (n = 94); and from those with two mismatches it was 50% (n = 4). The one-year graft survival rate in 25 donor-recipient pairs in which one or both members could not be satisfactorily DR typed was 76%. Differences in graft survival rates between the 0 and 1 and the 1 and 2 DR-mismatched groups were not statistically significant.(ABSTRACT TRUNCATED AT 400 WORDS)