HLA matching.

1. HLA matching exerts a profound influence on graft outcome. The difference in 3-year graft survival rates between best and worst matched cases was 17% for first grafts and 18% for retransplants. This HLA matching effect persists despite recent improvements in graft outcome. The matching effect at 3-years was 12% for transplants since 1991. 2. Surprisingly, HLA matching is especially important for recipients over age 60. The increase in the HLA matching effect to 20% in patients older than 60 can be attributed to the additive effects of HLA matching on both functional and patient survival. Consequently, graft survival for zero-MM recipients is similar for patients older and younger than age 60. 3. The difference in 3-year survival between zero and 0-MM kidneys was 10% for White and 15% for Black recipients. 4. Transplants with zero-broad but split A,B mismatches had graft outcomes similar to one-A,B,DR MM kidneys. Split DR MM did not affect the outcome of zero-MM kidneys. 5. HLA-matched transplants can be classified according to the degree of identity between the donor and recipient: 6-antigen match, phenotypic match, and zero-MM. Outcome for zero-MM was lower in transplants before 1990, but the 3 types have similar outcomes in recent transplants. The change in UNOS matching policy in 1995 to include zero-MM kidneys doubled the number of shared kidneys. 6. HLA typing from over 150 centers resulted in an error rate for shipped kidneys of less than 5%. Donor antigens retyped at the recipient center resulted in identical antigens for 70% of cases, a broad DR MM for 2.2%, and an A,B MM in 2.6% of the retyped cases. 7. Although increasing cold ischemia time (CIT) had a deleterious effect on survival of MM kidneys, no effect was seen for zero-MM kidneys. 8. An effect of a possible sex-linked minor histocompatibility antigen was demonstrated with improved outcome for male to male zero-MM cadaveric and parent-to-child transplants. 9. Zero-MM kidneys from pediatric donors and donors older than 60 years of age had poorer outcome than MM kidneys before 1991, but the recent experience shows a matching effect even with these marginal donors.