Inhibition of MLC responder and stimulator function with allo-antisera in rhesus monkeys

Ten antisera containing antibodies directed against specificities controlled by the Ia1 locus of rhesus monkeys were tested for their ability to inhibit the MLC reaction. In cultures with responding cells from the serum producer, all sera with anti-Ia1 activity depressed the stimulatory capacity of cells carrying the Ia1 antigen in question. In other responder/stimulator combinations, the stimulation-inhibition was Ia1-related for the majority of the antisera. These data provide further evidence for a possible identity (or close association on the cell membrane) between Ia1 and D locus determinants of rhesus monkeys. In addition, some sera showed an inhibitory effect also on responder cells (with cells from the serum producer as stimulators). There was no apparent relation of response inhibition to the Ia1 specificities detected by antisera.