MHC specified lymphocyte activating and suppressor activating determinants in human mixed lymphocyte reactions.

We have shown (1) the presence of HLA-linked Sad/s on a homozygous typing cell (HTC), FPA (8W321). When we used it to type the P family, which included an HLA-B/DR recombinant sibling, its genes mapped towards the HLA-B-A end of the HLA haplotype separate from HLA-D/DR and was found to be associated with HLA-Bw35 homozygosity; (2) this same recombinant maps the C4 complement genes on the HLA-D/DR end of the chromosome away from HLA-B; (3) that the suppressor T cell subpopulation which was activated by the Sad of this consanguineous HTC FPA was left behind after separating the OKT4 positive cells with a monomorphic monoclonal anti-T-cell antibody (OKT4). These OKT4 positive cells reacted normally in MLC to the FPA Lad Fes 6; (4) that at least part of the genetic control of suppressor recognition is outside the HLA complex.