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

The major subset of dendritic cells (DC) from bovine afferent lymph expresses the SIRPα 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)-1α, but not IL-1β, specific mAb. The proliferation of CD8+ T cells with CD11a+CC81+MyD-1− DC was also enhanced by adding IL-1α. IL-1β 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-1α synthesis by this population, which may have important consequences in vivo.