title: An essential role for IL-18 in CD8 T cell-mediated suppression of IgE responses.
abstract: The ability of CD8 T cells to suppress IgE responses is well established. Previously, we demonstrated that CD8 T cells inhibit IgE responses via the induction of IL-12, which promotes Th1 and suppresses Th2 responses. In this study, we show that IL-18 also plays an essential role in IgE suppression. In vitro, IL-18 synergized with IL-12 to promote Th1/T cytotoxic 1 and inhibit Th2/T cytotoxic 2 differentiation. OVA-specific TCR transgenic (OT-I) CD8 cells induced both IL-12 and IL-18 when cultured with OVA(257-264) peptide-pulsed dendritic cells. In vivo, IL-18(-/-) mice exhibited higher IgE and IgG1 levels compared with wild-type mice after immunization with OVA/alum. Furthermore, adoptive transfer of CD8 T cells from OVA-primed mice suppressed IgE responses in OVA/alum-immunized mice, but not in IL-18(-/-) mice. IgE suppression in IL-18(-/-) mice was restored if CD8 T cells were coadoptively transferred with IL-18-competent wild-type bone marrow dendritic cell progenitors, demonstrating an essential role of IL-18 in CD8 T cell-mediated suppression of IgE responses. The data suggest that CD8 T cells induce IL-18 production during a cognate interaction with APCs that synergizes with IL-12 to promote immune deviation away from the allergic phenotype. Our data identify IL-18 induction as a potentially useful target in immunotherapy of allergic disease.
authors.affiliation: Department of Asthma, Allergy, and Respiratory Science, King's College London School of Medicine, London, United Kingdom.
authors.forename: Maria
authors.initials: M
authors.lastname: Salagianni
authors.forename: Kok Loon
authors.initials: KL
authors.lastname: Wong
authors.forename: Wong Kok
authors.initials: WK
authors.lastname: Loon
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Thomas
authors.forename: Alistair
authors.initials: A
authors.lastname: Noble
authors.forename: David M
authors.initials: DM
authors.lastname: Kemeny
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D004357:Drug Synergism; D007108:Immune Tolerance; D007073:Immunoglobulin E / Q000097:blood*; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000494:pharmacology; D020382:Interleukin-18 / Q000494:pharmacology*; D015847:Interleukin-4 / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D020382:Interleukin-18; D018664:Interleukin-12; D015847:Interleukin-4; D007073:Immunoglobulin E; D007371:Interferon-gamma; D010047:Ovalbumin