title: Human thymocytes expressing gamma/delta T-cell receptors.
abstract: Expression of T-cell receptors of gamma/delta type characterizes a small subset of peripheral T lymphocytes which is homogeneously composed of cytolytic cells and, in most instances, lack CD4 and CD8 differentiation antigens. By the use of anti-TCR gamma/delta MAbs it is possible to identify two distinct subsets of TCR gamma/delta+ cells that are characterized by a C gamma 1 or C gamma 2-encoded forms of gamma-chain, respectively. While the BB3 MAb-reactive (C gamma 1 encoded) cell subset is prevalent in peripheral blood (PB), these cells represent less than 10% in TCR gamma/delta+ thymocyte populations. In thymus, the majority of cells was found to react with delta-TCSI (or A13) MAbs. Culture of CD4-8- thymocytes (highly enriched in TCR gamma/delta+ cells) in IL-2 resulted in the de novo expression of CD8 surface antigen and of non MHC-restricted cytolytic activity. Cloning of CD4-8- thymocytes resulted, for the most part, in CD3+ TCR gamma/delta+ cells. Moreover, the majority of clones expressed the unusual delta-TCSI+ CD8+ phenotype and lysed the NK-sensitive K562 target cells. Analysis of the immunoprecipitated TCR molecules showed the existence of the (rare) heavy (55 kDa) form of gamma-chain. A redirected killing assay using murine P815 target cells and appropriate "stimulatory" antibodies was further employed for functional analysis of thymus-derived TCR gamma/delta+ clones. While anti-CD3 MAbs efficiently triggered the cytolytic activity of all clones irrespective of their phenotype, MAbs directed to TCR gamma/delta induced efficient lysis only of BB3+ or delta-TCSI+CD8 clones, but not of delta-TCSI+ CD8+ clones.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy.
authors.forename: M C
authors.initials: MC
authors.lastname: Mingari
authors.forename: P
authors.initials: P
authors.lastname: Varese
authors.forename: C
authors.initials: C
authors.lastname: Bottino
authors.forename: G
authors.initials: G
authors.lastname: Tambussi
authors.forename: L
authors.initials: L
authors.lastname: Moretta
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D017252:CD3 Complex; D016827:CD8 Antigens; D002469:Cell Separation; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000502:physiology*; D016692:Receptors, Antigen, T-Cell, gamma-delta; D013601:T-Lymphocytes / Q000502:physiology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D016827:CD8 Antigens; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D016692:Receptors, Antigen, T-Cell, gamma-delta