title: Cytokine stimulation of T lymphocytes regulates their capacity to induce monocyte production of tumor necrosis factor-alpha, but not interleukin-10: possible relevance to pathophysiology of rheumatoid arthritis.
abstract: Previous studies in the laboratory have shown that the pro-inflammatory cytokine tumor necrosis factor (TNF)-alpha plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA). The mechanisms involved in regulating monocyte/macrophage cytokine production are not yet fully understood, but are thought to involve both soluble factors and cell/cell contact with other cell types. We and others have previously demonstrated that T cells activated through the T cell receptor/CD3 complex induce monocyte TNF-alpha production by contact-mediated signals. In this report, we investigated further whether T cells activated by cytokines in the absence of T cell receptor stimulation also regulate monocyte cytokine production. T cells were activated in an antigen-independent manner using the cytokines interleukin (IL)-15 or IL-2 alone, or in combination with IL-6 and TNF-alpha. Subsequently, T cells were fixed and incubated with monocytes. Fixed, cytokine-stimulated T cells induced monocytes to secrete TNF-alpha in a dose-dependent manner, but did not induce secretion of IL-10, a potent endogenous down-regulator of TNF-alpha and other pro-inflammatory cytokines. Stimulation of monocyte TNF-alpha was markedly inhibited when T cells were physically separated from monocytes within the tissue culture well, confirming that T cell contact is necessary. T cell acquisition of monocyte-activating capacity was shown to be dependent on the period of cytokine stimulation, with T cells activated for 8 days more effective than T cells activated for shorter periods. Addition of interferon-gamma or granulocyte/macrophage colony-stimulating factor to the T cell/monocyte cultures enhanced T cell induction of monocyte TNF-alpha by threefold and ninefold, respectively. The results from this model of cognate interaction suggest that cytokine-stimulated T cells, interacting with macrophages in the rheumatoid synovial membrane, may contribute to the continuous excessive production of TNF-alpha observed in the RA joint, and to the imbalance of pro-inflammatory cytokines over anti-inflammatory cytokines.
authors.affiliation: Kennedy Institute of Rheumatology, London, GB.
authors.forename: M
authors.initials: M
authors.lastname: Sebbag
authors.forename: S L
authors.initials: SL
authors.lastname: Parry
authors.forename: F M
authors.initials: FM
authors.lastname: Brennan
authors.forename: M
authors.initials: M
authors.lastname: Feldmann
mesh_terms: D000954:Antigens, Surface / Q000032:analysis; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D002450:Cell Communication; D002478:Cells, Cultured; D016207:Cytokines / Q000502:physiology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D016130:Immunophenotyping; D007371:Interferon-gamma / Q000494:pharmacology; D016753:Interleukin-10 / Q000276:immunology*; D019409:Interleukin-15 / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000494:pharmacology
chemical_list: D000954:Antigens, Surface; D016207:Cytokines; D019409:Interleukin-15; D007376:Interleukin-2; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor