Fc Receptors on Human T-Lymphocytes

Abstract

Abstract After in vitro allosensitization, human peripheral blood lymphocytes mediate specific allogeneic cell-mediated lysis (CML) and antibody-dependent cellular cytotoxicity (ADCC). To analyze the T lymphocyte subpopulations involved in CML and ADCC, lymphocytes were separated on the basis of their affinity for sheep erythrocytes (T cells), for Fc-IgM (TM cells), and Fc-IgG (TG cells) either before or after allosensitization. Subpopulations of T cells highly enriched for TM cells generated CML comparable to unseparated T cells, but subpopulations enriched for TG and effectively depleted of TM cells did not generate strong CML. Studies of CML generation by T cells exposed to immune complexes and by cocultured TM and TG cells failed to demonstrate any suppression by TG cells. Separation of subpopulations after allosensitization revealed that CML activity was mediated by T cells that lacked detectable Fc-IgG or Fc-IgM receptors. Parallel studies of ADCC revealed that the cytotoxic activity was depleted by removal of TG cells either before or after allosensitization. These studies demonstrate that a) TM cells contain precursors of CML effectors; b) TG cells are not required for the generation of CML; c) TG cells do not have marked suppressor activity in CML generation; d) TG cells contain ADCC effectors; and e) TM cells are not required for ADCC.