Mixed-lymphocyte culture response in a related and an unrelated Australian population

In 256 related combinations in an Australian Caucasian population, the relative responses in one-way mixed-lymphocyte cultures can be divided into four different groups: (i) HLA zero-haplotype different; (ii) HLA-D homozygous-versus-heterozygous; (iii) HLA one-haplotype different: and (iv) HLA two-haplotype different. The median relative responses of the groups were 0.78%, 20%, 64% and 86.5%, respectively; 17.7% of HLA-A, HLA-B identical siblings were found to stimulate significantly in mixed-lymphocyte culture, and 6.3% of HLA one-haplotype different combinations had weak responses. The median relative response of 225 unrelated random combinations was 100%. One mixed-lymphocyte culture combination in this group gave a relative response of 20%, which was found to be a HLA-D homozygous-versus-heterozygous response. A relative response of 20% in mixed-lymphocyte cultures may be taken to indicate relative HLA-D compatibility and would, therefore, predict a favourable outcome in kidney transplantation. The use of mixed-lymphocyte cultures as a routine in selecting suitable donors in living related transplants and, retrospectively, in monitoring the results of cadaveric transplants, is advocated.