title: The CD4-centered universe of human T cell subsets.
abstract: Humans are continuously exposed to a high number of diverse pathogens that induce different types of immune responses. Primary pathogen-specific immune responses generate multiple subsets of memory T cells, which provide protection against secondary infections. In recent years, several novel T cell subsets have been identified and have significantly broadened our knowledge about T cell differentiation and the regulation of immune responses. At the same time the rapidly growing number of incompletely characterized T cell subsets has also generated some controversies. We therefore review here the current knowledge on features and functions of human α/β T cell subsets, focusing on CD4(+) T cells classified according to cytokine production and tissue localization. The principal helper and regulatory T cell subsets can be identified by a limited number of relevant surface markers, which are an integral part of the T cell differentiation programs because they are directly induced by the relevant lineage-defining transcription factors. In vivo occurring human T cell subsets can thus be purified directly ex vivo from relevant tissues for molecular and functional studies, and represent not only an ideal model to study T cell differentiation, but they also offer important clinical opportunities.
authors.affiliation: Istituto Nazionale di Genetica Molecolare (INGM), Autoimmunity Program, Via Sforza 35, 20122 Milan, Italy. Electronic address: geginat@ingm.org.
authors.forename: J
authors.initials: J
authors.lastname: Geginat
authors.forename: M
authors.initials: M
authors.lastname: Paroni
authors.forename: F
authors.initials: F
authors.lastname: Facciotti
authors.forename: P
authors.initials: P
authors.lastname: Gruarin
authors.forename: I
authors.initials: I
authors.lastname: Kastirr
authors.forename: F
authors.initials: F
authors.lastname: Caprioli
authors.forename: M
authors.initials: M
authors.lastname: Pagani
authors.forename: S
authors.initials: S
authors.lastname: Abrignani
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D016130:Immunophenotyping; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000378:metabolism
chemical_list: D000954:Antigens, Surface; D016207:Cytokines
keywords: CD4(+) memory T cells; Cytokines; T cell differentiation; Tissue homing