title: Cellular and molecular mechanisms of activation of MHC nonrestricted cytotoxic cells by IL-12.
abstract: Freshly separated PBL and two IL-2-dependent clonal T cell lines (TALL-103/2 [TCR-gamma delta+] and TALL-104 [TCR-alpha beta+]) were used to dissect, at the cellular and molecular levels, the mechanisms governing the enhancing effects of IL-12 on MHC nonrestricted cytotoxic activity. IL-12 induced cytotoxicity both in PBL and TALL cells, although less efficiently than IL-2, and the two cytokines displayed additive effects. Unlike IL-2, IL-12 failed to enhance the CD3 or CD2 redirected killing of the TALL cell lines. Analysis of the percentage of E/T conjugates induced by these cytokines showed that IL-12 could increase PBL, but not TALL cell, binding only when used in combination with IL-2. This and the failure of IL-12 to increase the expression of several adhesion molecules on PBL and TALL cells indicated no significant role for IL-12 in the binding step of the lytic interaction. We also excluded that production of TNF-alpha, IFN-gamma, or IL-2 by the IL-12-activated effectors might account for the cytotoxicity-inducing effects of this cytokine. By contrast, IL-12 was found to induce cytotoxic granule formation in PBL and TALL cells and to up-regulate the expression of their cytolytic components, including perforin, serine esterases, and TIA-1, both at the protein and mRNA levels. The costimulatory action of IL-2 and IL-12 on granulogenesis and induction of cytolytic proteins correlated well with the additive effects on cytotoxicity. Studies with cyclohexamide and actinomycin D demonstrated that TALL cells but not PBL require de novo protein synthesis for expression of serine esterases and perforin mRNA after IL-2 and/or IL-12 stimulation, and that both cytokines act directly or indirectly at the transcriptional level. Overall, these data indicate that IL-12 acts mostly at a postbinding level of the lytic interaction, involving enhanced expression of cytotoxic mediators, and that IL-2 and IL-12 use partially distinct pathways to activate the MHC nonrestricted killer function of mature T cells and resting lymphocytes.
authors.affiliation: Wistar Institute of Anatomy and Biology, Philadelphia, PA 19104.
authors.forename: A
authors.initials: A
authors.lastname: Cesano
authors.forename: S
authors.initials: S
authors.lastname: Visonneau
authors.forename: S C
authors.initials: SC
authors.lastname: Clark
authors.forename: D
authors.initials: D
authors.lastname: Santoli
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D015870:Gene Expression / Q000187:drug effects; D053804:Granzymes; D006801:Humans; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000494:pharmacology; D018664:Interleukin-12; D007376:Interleukin-2 / Q000494:pharmacology; D007378:Interleukins / Q000494:pharmacology*; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects*; D008285:Major Histocompatibility Complex; D008562:Membrane Glycoproteins / Q000235:genetics; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins; D012697:Serine Endopeptidases / Q000235:genetics; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D015815:Cell Adhesion Molecules; D007376:Interleukin-2; D007378:Interleukins; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D054353:Perforin; C073187:HP-10 protein, human; D018664:Interleukin-12; D007371:Interferon-gamma; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases; C509212:GZMA protein, human