title: IL-10 production is enhanced in human T cells by IL-12 and IL-6 and in monocytes by tumor necrosis factor-alpha.
abstract: IL-10, an immunoregulatory cytokine produced by T cells and monocytes, inhibits the expression of inflammatory and hemopoietic cytokines as well as its own expression. To evaluate the regulation of IL-10 production by T cells and monocytes, we measured IL-10 levels by ELISA in supernatants of PHA-stimulated PBMC following depletion of either T cells or monocytes. IL-10 production was significantly down-regulated in both T cell- and monocyte-depleted PBMC compared with undepleted PBMC, and IL-10 production could be restored by the addition of monocyte-conditioned medium (supernatant of PHA-stimulated, T cell-depleted PBMC), suggesting that IL-10 production by T cells is regulated by a monokine(s) produced by activated monocytes. To further clarify the monokine(s) responsible for IL-10 induction, we stimulated monocyte-depleted PBMC, purified CD4+, and CD8+ T cells with PHA and measured IL-10 production by ELISA and semiquantitative reverse transcriptase-PCR following monokine(s) addition. Addition of IL-6 and IL-12 enhanced IL-10 production in monocyte-depleted PBMC in a dose-dependent and additive manner. Furthermore, anti-IL-6 and anti-IL-12 Abs neutralized the IL-10-inductive effect of monocyte-conditioned medium. Similarly, IL-12 and IL-6 induced IL-10 production by purified CD4+ and CD8+ T cells. With respect to regulation of IL-10 produced by monocytes, TNF-alpha was found to induce IL-10 production by resting as well as by LPS-stimulated purified monocytes/macrophages. Taken together, these findings suggest that IL-10 production by human T cells and monocytes is differentially regulated. IL-12 and/or IL-6 can induce the expression of IL-10 by PHA-stimulated T cells, whereas TNF-alpha induces IL-10 production by monocytes. Since IL-10 inhibits the production of IL-6, IL-12, and TNF-alpha, these results may indicate a potential mechanism of negative feedback regulation of the immune response.
authors.affiliation: Department of Pediatrics, University of Ottawa, Ontario, Canada.
authors.forename: P M
authors.initials: PM
authors.lastname: Daftarian
authors.forename: A
authors.initials: A
authors.lastname: Kumar
authors.forename: M
authors.initials: M
authors.lastname: Kryworuchko
authors.forename: F
authors.initials: F
authors.lastname: Diaz-Mitoma
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D016753:Interleukin-10 / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D007700:Kinetics; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008969:Molecular Sequence Data; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000276:Adjuvants, Immunologic; D015850:Interleukin-6; D010835:Phytohemagglutinins; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D018664:Interleukin-12