title: Interleukin-4-mediated downregulation of cytotoxic T lymphocyte activity is associated with reduced proliferation of antigen-specific CD8+ T cells.
abstract: During virus infection, exogenous IL-4 strongly downregulates expression of antiviral cytokines and cytotoxic T lymphocyte (CTL) responses. In this study, we have employed a T cell receptor (TCR) transgenic system to more closely investigate the effect of IL-4 on CTL activity. This system involves mice transgenic for an H2-Kb restricted TCR recognising an ovalbumin (OVA)-specific peptide (OT-I mice), and recombinant vaccinia viruses expressing the gene for OVA (VV-OVA), or OVA together with IL-4 (VV-OVA-IL-4). Spleen cells from OT-I mice were adoptively transferred to irradiated C57BL/6 mice infected with VV-OVA or VV-OVA-IL-4. Five days following transfer, markedly stronger CTL activity was detected in VV-OVA- than in VV-OVA-IL-4-infected recipients. The reduction in CTL activity was associated with a reduction in the number of OVA-specific CD8+ T cells. Proliferation of cells from VV-OVA-IL-4-infected recipients was dramatically reduced, and this is a likely explanation for the IL-4-mediated reduction in the total number of OVA-specific cells and the reduced cytotoxic activity. On a per cell basis, the production of IFNgamma and cytotoxic activity of OVA-specific CD8+ cells was not influenced by IL-4. Taken together, our results indicate that the reduction in CTL activity by exogenous IL-4 is due to a reduced number of antigen-specific effectors, and does not involve a downregulation of effector function of these cells.
authors.affiliation: Division of Immunology and Cell Biology, John Curtin School of Medical Research, P.O. Box 334, Canberra, ACT 2601, Australia. m.rolph@garvan.org.au
authors.forename: Michael S
authors.initials: MS
authors.lastname: Rolph
authors.forename: Ian A
authors.initials: IA
authors.lastname: Ramshaw
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D000941:Antigens / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000276:immunology; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D015536:Down-Regulation; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology; D015847:Interleukin-4 / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D051379:Mice; D010047:Ovalbumin / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014616:Vaccinia virus / Q000276:immunology / Q000502:physiology
chemical_list: D000941:Antigens; D015847:Interleukin-4; D007371:Interferon-gamma; D010047:Ovalbumin