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Inflammatory cytokines provide a third signal for activation of naive CD4+ and CD8+ T cells
J M Curtsinger1, C S Schmidt, A Mondino
1Center for Immunology, University of Minnesota, Minneapolis 55455, USA.
The effects of inflammatory cytokines on naive T cells have been studied using MHC protein/peptide complexes on microspheres, thus avoiding the use of APCs whose functions may be affected by the cytokines. IL-1, but not IL-12, increased proliferation of CD4+ T cells in response to Ag and IL-2, which is consistent with effects on in vivo priming of CD4+ cells. In contrast, proliferation of CD8+ T cells to Ag and IL-2 required IL-12, and IL-12 replaced adjuvant in stimulating an in vivo response to peptide. These results support a model in which distinct inflammatory cytokines act directly on naive CD4+ and CD8+ T cells to provide a third signal, along with Ag and IL-2, to optimally activate differentiation and clonal expansion.
The effects of inflammatory cytokines on naive T cells have been studied using MHC protein/peptide complexes on microspheres, thus avoiding the use of APCs whose functions may be affected by the cytokines. IL-1, but not IL-12, increased proliferation of CD4+ T cells in response to Ag and IL-2, which is consistent with effects on in vivo priming of CD4+ cells. In contrast, proliferation of CD8+ T cells to Ag and IL-2 required IL-12, and IL-12 replaced adjuvant in stimulating an in vivo response to peptide. These results support a model in which distinct inflammatory cytokines act directly on naive CD4+ and CD8+ T cells to provide a third signal, along with Ag and IL-2, to optimally activate differentiation and clonal expansion.