Effect of blood-group on relation between HLA match and outcome of cadaver kidney transplants

In a series of 4998 cadaver kidney transplants the extent of HLA matching correlated with transplant outcome in patients with blood-groups other than O (non-O) but not in patients of blood-group O. The high survival-rate of poorly matched kidneys in O recipients was responsible for the lack of correlation between HLA matching and graft survival in these patients. Survival-rates of transplants with 4 HLA mismatches were 52 +/- 3% at one year in 222 O-to-O grafts compared with 24 +/- 5% in 65 B-to-B grafts (P less than 0.0001). In 2827 non-O patients, there was a strong correlation between HLA matching and graft survival (P less than 0.0001 at one year). One possible reason for the cancelling out of the effect of HLA mismatching in type-O recipients is that these patients waited longer on dialysis for a transplant and consequently received more blood-transfusions.