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 subpopulations 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.