Differences in the induction of CD8+ T cell responses by subpopulations of dendritic cells from afferent lymph are related to IL-1 alpha secretion

The major subset of dendritic cells (DC) from bovine afferent lymph expresses the SIRP alpha MyD-1 antigen, but not CD11a or the antigen recognized by mAb CC81, and potently stimulates CD4+ and CD8+ T lymphocyte proliferation. The minor subpopulation, that is CD11a+ CC81+ MyD-1-, effectively stimulates CD4+ but not CD8+ T lymphocyte proliferation. CD11a+ CC81+ MyD-1- DC did not induce anergy or death or secrete an inhibitory factor. However, supernatant from cultures of CD8+ T cells with CD11a- CC81- MyD-1+ DC significantly enhanced proliferation of CD8+ T cells in response to CD11a+ CC81+ MyD-1- DC, an effect that was blocked by interleukin (IL)-1alpha, but not IL-1beta, specific mAb. The proliferation of CD8+ T cells with CD11a+ CC81+ MyD-1- DC was also enhanced by adding IL-1alpha. IL-1beta slightly enhanced proliferation, whereas IL-2, IL-6, IL-12, and IL-15 had no effect. We conclude that the failure to stimulate CD8+ T cell proliferation results from the lack of IL-1alpha synthesis by this population, which may have important consequences in vivo.