title: The CD4+ T-cell response to protein immunization is independent of accompanying IFN-gamma-producing CD8+ T cells.
abstract: By virtue of their strong bias towards production of interferon-gamma (IFN-gamma), CD8+ T cells have the potential to promote the development of type 1 immune responses. We have previously shown that the CD4+ T-cell response to immunization with the protein antigen keyhole limpet haemocyanin (KLH) has a mixed interleukin-4 (IL-4)/IFN-gamma production profile. Here we show that this immunization regimen also stimulates accumulation in the draining lymph nodes of CD8+ T cells, which preferentially contain IFN-gamma mRNA ex vivo and secrete IFN-gamma protein in vitro. This provides a model to test whether CD8+ cell-derived IFN-gamma participates in the normal control of the immune response to a non-viable exogenous antigen. To investigate regulation of the anti-KLH response by the CD8+ population or IFN-gamma produced by this or other cell types, mice were administered depleting antibodies. Depletion of CD8+ cells had no effect on the frequency of clonogenic KLH-specific CD4+ T cells, the IL-4/IFN-gamma profiles of their progeny, or the isotype profiles of the serum antibody response to KLH. In contrast, IFN-gamma neutralization diminished cell accumulation in the lymph nodes and reduced both the frequency of KLH-specific CD4+ T cells that gave rise to IFN-gamma-producing clones and serum titres of KLH-specific IgG2a and IgG3. Therefore, despite the potential for cross-regulation, the CD4+ T-cell response to this immunogen is independent of the IFN-gamma-skewed CD8+ response.
authors.affiliation: Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Queensland, Australia.
authors.forename: A G
authors.initials: AG
authors.lastname: Doyle
authors.forename: L
authors.initials: L
authors.lastname: Ramm
authors.forename: A
authors.initials: A
authors.lastname: Kelso
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005260:Female; D006433:Hemocyanins / Q000494:pharmacology*; D007371:Interferon-gamma / Q000378:metabolism*; D015847:Interleukin-4 / Q000378:metabolism; D008213:Lymphocyte Activation; D008212:Lymphocyte Depletion; D051379:Mice; D008810:Mice, Inbred C57BL; D018448:Models, Immunological; D013997:Time Factors
chemical_list: D000939:Epitopes; D015847:Interleukin-4; D007371:Interferon-gamma; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin