Role of MLC compatibility in intrafamilial kidney transplantation.

The role of compatibility at the HL-A and mixed lymphocyte culture (MLC) loci for graft survival was analysed in 45 recipients of intrafamilial kidneys. MLC tests performed after transplantation when the recipients were on maintenance immunosuppressive therapy did not show a reduced reactivity of the recipient lymphocytes as compared to tests performed before surgery. The results with the two-way MLC test was paradoxical: patients with functioning grafts had a higher mean stimulation than did those with nonfunctioning grafts. Subsequent clinical correlations were based on one-way MLC carried out before or after transplantation. The 1-year survival of grafts from HL-A compatible donors was 94% and that of graft from HL-A incompatible donors was 75%. When the comparison was between grafts from MLC-negative and MLC-positive donors the figures were 100 and 75%, respectively. If the cases were divided in those displaying a low relative reactivity (RR), indicating identity at the major (LD-1, HL A-D) MLC locus, towards their donors in MLC and those with a high RR, the graft survival was 100% versus 70% (P less than 0.05). The prognosis seemed to be worse the higher the relative reactivity. At 3 years all grafts from donors with negative reaction or low RR in the MLC were still functioning. Analysis of the few exceptional cases in which there was compatibility for either the HL-A or MLC locus but not for the other points to the major MLC locus as being most important for graft survival.