title: A unique T-cell receptor complex expressed on human fetal lymphocytes displaying natural-killer-like activity.
abstract: We have recently derived a series of cloned cell lines displaying natural killer (NK) cell-like activity from normal human fetal blood (25 weeks). The lines were obtained after repeated stimulation of mononuclear cells with allogeneic Epstein-Barr virus (EBV)-transformed B lymphocytes and are interleukin-2 (IL-2) dependent. Initial characterization of the clones has been reported previously. Certain of these clones have been found to have unusual surface characteristics, namely, they are recognized by several well-defined anti-T3 antibodies, but do not react with WT31, which is thought to recognise an invariant epitope of the human (Ti-alpha beta) structure. Transcription of the genes encoding the alpha- and beta-chains of the T-cell receptor was assessed in two of these clones (F6A4 and F6C7). Ti-beta genes were found to be expressed, whereas alpha messenger RNA was not detected in Northern blot analysis. These data strongly suggest that these cells do not produce a stoichiometric T3/Ti-alpha beta receptor complex. However, experiments performed with a monoclonal antibody (anti-NKFi) developed against F6C7 cells demonstrated the existence of a unique clonotypic structure [relative molecular mass (Mr) 85,000 (85K)] which is surface-associated with T3 proteins. Furthermore, both anti-T3 and anti-NKFi were found to block cytotoxic effector function. Together, the results support the view that T3 proteins are involved in non-major histocompatibility complex (MHC)-restricted cytotoxic reactions mediated by certain circulating fetal lymphocytes which are likely to use a clonotypic structure distinct from both the 'first' (alpha beta) and the putative 'second' (gamma delta) T-cell receptor to recognize their target. The present studies were designed to characterize this structure.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology; D002454:Cell Differentiation; D002460:Cell Line; D003602:Cytotoxicity, Immunologic; D005312:Fetal Blood / Q000276:immunology*; D005786:Gene Expression Regulation; D006801:Humans; D007111:Immunity, Cellular; D007152:Immunologic Capping; D007694:Killer Cells, Natural / Q000502:physiology*; D008214:Lymphocytes / Q000502:physiology*; D046911:Macromolecular Substances; D012333:RNA, Messenger / Q000235:genetics; D011948:Receptors, Antigen, T-Cell / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D046911:Macromolecular Substances; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell