title: Interleukin 12 induces stable priming for interferon gamma (IFN-gamma) production during differentiation of human T helper (Th) cells and transient IFN-gamma production in established Th2 cell clones.
abstract: Interleukin 12 (IL-12) facilitates the generation of a T helper type 1 (Th1) response, with high interferon gamma (IFN-gamma) production, while inhibiting the generation of IL-4-producing Th2 cells in polyclonal cultures of both human and murine T cells and in vivo in the mouse. In this study, we analyzed the effect of IL-12, present during cloning of human T cells, on the cytokine profile of the clones. The culture system used allows growth of clones from virtually every T cell, and thus excludes the possibility that selection of precommitted Th cell precursors plays a role in determining characteristics of the clones. IL-12 present during the cloning procedures endowed both CD4+ and CD8+ clones with the ability to produce IFN-gamma at levels severalfold higher than those observed in clones generated in the absence of IL-12. This priming was stable because the high levels of IFN-gamma production were maintained when the clones were cultured in the absence of IL-12 for 11 d. The CD4+ and some of the CD8+ clones produced variable amounts of IL-4. Unlike IFN-gamma, IL-4 production was not significantly different in clones generated in the presence or absence of IL-12. These data suggest that IL-12 primes the clone progenitors, inducing their differentiation to high IFN-gamma-producing clones. The suppression of IL-4-producing cells observed in polyclonally generated T cells in vivo and in vitro in the presence of IL-12 is not observed in this clonal model, suggesting that the suppression depends more on positive selection of non-IL-4-producing cells than on differentiation of individual clones. However, antigen-specific established Th2 clones that were unable to produce IFN-gamma with any other inducer did produce IFN-gamma at low but significant levels when stimulated with IL-12 in combination with specific antigen or insoluble anti-CD3 antibodies. This induction of IFN-gamma gene expression was transient, because culture of the established clones with IL-12 for up to 1 wk did not convert them into IFN-gamma producers when stimulated in the absence of IL-12. These results suggest that Th clones respond to IL-12 treatment either with a stable priming for IFN-gamma production or with only a transient low level expression of the IFN-gamma gene, depending on their stage of differentiation.
authors.affiliation: Division of Clinical Immunology and Allergy, University of Florence, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Manetti
authors.forename: F
authors.initials: F
authors.lastname: Gerosa
authors.forename: M G
authors.initials: MG
authors.lastname: Giudizi
authors.forename: R
authors.initials: R
authors.lastname: Biagiotti
authors.forename: P
authors.initials: P
authors.lastname: Parronchi
authors.forename: M P
authors.initials: MP
authors.lastname: Piccinni
authors.forename: S
authors.initials: S
authors.lastname: Sampognaro
authors.forename: E
authors.initials: E
authors.lastname: Maggi
authors.forename: S
authors.initials: S
authors.lastname: Romagnani
authors.forename: G
authors.initials: G
authors.lastname: Trinchieri
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology; D016827:CD8 Antigens / Q000276:immunology; D002454:Cell Differentiation; D002999:Clone Cells / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000276:immunology; D018664:Interleukin-12; D015847:Interleukin-4 / Q000096:biosynthesis; D007378:Interleukins / Q000502:physiology*; D051379:Mice; D006377:T-Lymphocytes, Helper-Inducer / Q000166:cytology* / Q000378:metabolism
chemical_list: D000906:Antibodies; D017252:CD3 Complex; D015704:CD4 Antigens; D016827:CD8 Antigens; D007378:Interleukins; D018664:Interleukin-12; D015847:Interleukin-4; D007371:Interferon-gamma