title: IFN-gamma but not IL-4 is important for mouse CD4+ T cell-mediated macrophage activation following their exposure to pig cells in vitro.
abstract: In order to investigate the mechanism by which CD4+ T cells and macrophages interact in the xenogeneic immune response, murine CD4+ T cells and macrophages were used as responder cells in culture with irradiated fetal pig spleen cells (FPSC) as pig xenogeneic stimulators. In this in vitro model, murine CD4+ T cells and macrophages were cultured individually, or together with FPSC. In addition, mouse CD4+ T cells were also cultured with autologous macrophages which were previously stimulated by FPSC. The cultured murine cells were analyzed for expression of CD4+ T cell and macrophage activation markers (cell surface markers and cytokines) as well as cytokine production. CD4+ T cells and macrophages cultured alone or together without FPSC showed unchanged low levels of expression of activation markers. Coculture of macrophages with FPSC and in the absence of CD4+ T cells induced increased expression levels of all the activation markers examined except B7.2 and ICAM-1. Addition of CD4+ T cells to the coculture further enhanced this up-regulation. Coculture of CD4+ T cells with FPSC-stimulated macrophages, but not naive macrophages, or FPSC alone, resulted in significantly increased numbers of CD4+ T cells coexpressing their activation markers, especially IFN-gamma and CD40L, and this expression was enhanced further by including FPSC in the coculture. The activation of both CD4+ T cells and macrophages in their coculture with FPSC was suppressed by neutralizing IFN-gamma but not IL-4. Our results demonstrated that interaction of CD4+ T cells and autologous macrophages was required for their optimal activation in response to pig xenogeneic stimulation. The mechanisms involved included cell-cell and/or cytokine interactions, and in particular IFN-gamma mediated communication was involved. Macrophages activated by pig cells in the absence of CD4+ T cells were able to activate naive CD4+ T cells, thus providing an important communication pathway between innate immune activation and a T cell mediated response in xenograft rejection.
authors.affiliation: National Pancreas Transplant Unit, University of Sydney at Westmead Hospital, Westmead, NSW, Australia. philip_oconnell@wsahs.nsw.gov.au
authors.forename: Shounan
authors.initials: S
authors.lastname: Yi
authors.forename: Philip J
authors.initials: PJ
authors.lastname: O'Connell
mesh_terms: D000818:Animals; D000917:Antibody Formation; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000032:analysis; D017931:DNA Primers; D016332:Fetal Tissue Transplantation / Q000276:immunology; D005434:Flow Cytometry; D007371:Interferon-gamma / Q000235:genetics* / Q000494:pharmacology*; D015847:Interleukin-4 / Q000235:genetics*; D008262:Macrophage Activation / Q000187:drug effects / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D014183:Transplantation, Heterologous / Q000276:immunology*
chemical_list: D016207:Cytokines; D017931:DNA Primers; D015847:Interleukin-4; D007371:Interferon-gamma