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 (T_p), and cell-mediated cytolysis (CMC) measures the cytotoxic T cells (T_c) generated, which can destroy tissue cells bearing the alloantigens against which the response is directed¹. T_p and T_c are thought to be derived from different precursors, the T_P-P and T_C-P respectively, and each seem to have different requirements for activation. Initially it was claimed that T_P-P and T_C-P were coded to respond to antigens specified by different genes in the MHC² but this distinction has since been shown not to be absolute^3–6. We previously demonstrated⁷ that T_P-P and T_C-P had different antigen-binding characteristics as T_C-P could be bound in a haplotype-specific manner to allogeneic monolayers but T_P-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 T_P-P will bind only when self- plus alloantigen are presented by a monolayer, whereas T_C-P will bind when alloantigen alone is present.