title: The human T-cell circuit.
abstract: Recent studies have helped to rapidly advance our understanding of the human T lymphocyte, particularly with regard to the heterogeneity of T-cell subpopulations and the characterization of surface determinants on these cells that function as important membrane receptors. With the use of monoclonal antibodies, it is possible to identify cell-surface antigens which appear during T-cell ontogeny and by which functionally and phenotypically distinct subsets of T cells can be distinguished. Within the mature T4+ subset, which is responsible for inducer/helper functions in T-T, T-B, and T-macrophage interactions, are discrete subpopulations responsible for the induction of help for antibody production and for the induction of T8+ suppressor effector cells. Within the T8+ subset are precursor and effector cells responsible for suppressive or cytotoxic activity. For a wide variety of cellular interactions (including the sensitization of cytotoxic effector cells), it is now evident that T4 cells show a preferential interaction with class II MHC determinants on accessory or target cells, whereas T8 cells have a preference for class I determinants. Moreover, the T4 and T8 glycoproteins themselves may function as associative recognition structures in such interactions. Recent work has elucidated the role of the T3-Ti antigen receptor complex. The T3 molecule, a nonpolymorphic determinant, is membrane-associated with the 90 KD Ti heterodimer, a highly polymorphic structure with both constant and variable regions, that represents the T-cell receptor for antigen.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D002999:Clone Cells; D006801:Humans; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex; D013601:T-Lymphocytes / Q000145:classification / Q000166:cytology / Q000276:immunology*