The effect of HLA matching on kidney graft survival in separate posttransplantation intervals.

The effect of matching for the HLA antigens has been well established as important in the prognosis of kidney grafts. By analyzing the effect of matching on first transplants from unrelated donors in specific intervals up to 3 years posttransplantation, we show that the effect of HLA-DR matching is strongest in the first 5 months following transplantation (relative risks of graft failure 1.31 and 1.77 for 1 and 2 HLA-DR mismatches, respectively, compared with no mismatches). For patients whose grafts remained functioning after 5 months, there was no significant further improvement in graft survival to 3 years (relative risks 1.16 and 0.98 for 1 and 2 HLA-DR mismatches, respectively, compared with no mismatches)--i.e., the gain in graft survival by matching for HLA-DR appears to be due to its influence in the first 5 months following transplantation. For HLA-B, the matching effect was evident both before and after 5 months (relative risks 1.11 and 1.27 for 1 and 2 HLA-B mismatches, respectively, compared with no mismatches and modelled as constant over the 3-year period), whereas no effect of HLA-A matching was evident in the period up to 3 years.