Early recognition of transplantation antigens by T lymphocytes. II. Specificity and characterization of the recognition process.

Abstract

In crude supernates of interactions of parental strain T spleen cells with H-2 antigen-bearing F1 hybrid spleen cells, a product (soluble early product of immune recognition, SEPIR) can be found which enhances mixed leukocyte culture (MLC) reactions set up with suboptimal cell concentrations (SMLC). Supernates of parental T cells reacting with F1 spleen cell also produce this factor. The product ameliorates SMLC proliferative responses specifically since identical antigenic specificities have to be recognized in both SEPIR formation and in test SMLC. Further evidence for SEPIR being an immunologically specific product is documented by the finding that spleen cells from mice made specifically tolerant at birth cannot respond to the tolerogen with SEPIR formation, but are fully reactive towards unrelated H-2 antigens. No responses to syngeneic or autologous antigens could be discerned. Characterization of allorecognition resulting in SEPIR formation has revealed that spleen cells of Lyt 23 phenotype recognize H-2K/D-encoded antigens. Lyt 1 cells appear to be incapable of forming the early product and H-2I-determined antigens fail to incite a response. Reactivity to class I antigens was amenable to specific inhibition by monoclonal alloantibodies.