Binding of MLR precursors requires immunosorbents which present both self- and alloantigen

Abstract

The response of T lymphocytes to antigens of the major histo-compatibility complex (MHC) in a species is commonly measured by two assays. The mixed lymphocyte reaction (MLR) measures proliferating lymphocytes (Tp), and cell-mediated cytolysis (CMC) measures the cytotoxic T cells (Tc) generated, which can destroy tissue cells bearing the alloantigens against which the response is directed1. Tp and Tc are thought to be derived from different precursors, the TP-P and TC-P respectively, and each seem to have different requirements for activation. Initially it was claimed that TP-P and TC-P were coded to respond to antigens specified by different genes in the MHC2 but this distinction has since been shown not to be absolute3–6. We previously demonstrated7 that TP-P and TC-P had different antigen-binding characteristics as TC-P could be bound in a haplotype-specific manner to allogeneic monolayers but TP-P were not bound in these conditions. We report here further experiments which show that these two populations have qualitatively distinct antigen recognition properties, by demonstrating that TP-P will bind only when self- plus alloantigen are presented by a monolayer, whereas TC-P will bind when alloantigen alone is present.