title: Phenotypic and functional analysis of positive selection in the gamma/delta T cell lineage.
abstract: Recent evidence suggests that T cells expressing gamma/delta antigen receptors (T cell receptor [TCR]) are subject to positive selection during development. We have shown that T cells expressing a class I major histocompatibility complex (MHC)-specific gamma/delta TCR transgene (tg) are not positively selected in class I MHC-deficient, beta 2-microglobulin (beta 2m) gene knockout mice (tg+ beta 2m-). In this report, we examine phenotypic and functional parameters of gamma/delta positive selection in this transgenic model system. TCR-gamma/delta tg+ thymocytes of mature surface phenotype (heat stable antigen-, CD5hi) were found in beta 2m+ but not in beta 2m- mice. Moreover, subsets of tg+ thymocytes with the phenotype of activated T cells (interleukin [IL]2R+, CD44hi, or Mel-14lo) were also present only in the beta 2m+ mice. Cyclosporine A, which blocks positive selection of TCR-alpha/beta T cells, also inhibited gamma/delta tg+ T cell development. These results support the idea that positive selection of TCR-gamma/delta requires active TCR-mediated signal transduction. Whereas tg+ beta 2m+ thymocytes produced IL-2 and proliferated when stimulated by alloantigen, TCR engagement of tg+ beta 2m- thymocytes by antigen induced IL-2R expression but was uncoupled from the signal transduction pathway leading to IL-2 production and autocrine proliferation. Overall, these results demonstrate significant parallels between gamma/delta and alpha/beta lineage development, and suggest a general role for TCR signaling in thymic maturation.
authors.affiliation: Biological Carcinogenesis and Development Program, PRI/DynCorp, Frederick, Maryland 21702-1201.
authors.forename: F B
authors.initials: FB
authors.lastname: Wells
authors.forename: Y
authors.initials: Y
authors.lastname: Tatsumi
authors.forename: J A
authors.initials: JA
authors.lastname: Bluestone
authors.forename: S M
authors.initials: SM
authors.lastname: Hedrick
authors.forename: J P
authors.initials: JP
authors.lastname: Allison
authors.forename: L A
authors.initials: LA
authors.lastname: Matis
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D016572:Cyclosporine / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010641:Phenotype; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects / Q000254:growth & development
chemical_list: D016692:Receptors, Antigen, T-Cell, gamma-delta; D016572:Cyclosporine