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 express es the SIRP alpha MyD-1 antigen, but not CD11a or the antigen recognized by mAb CC81, and potently stimulates CD4(+) and CD8(+) T lymphocyte prolifera tion, 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 facto r. However, supernatant from cultures of CD8(+) T cells with CD11a(-)CC81(- )MyD-1(+) DC significantly enhanced proliferation of CD8(+) T cells in resp onse to CD11a(+)CC81(+)MyD-1(-) DC, an effect that was blocked by interleuk in (IL)-1 alpha, but not IL-1 beta, specific mAb. The proliferation of CD8( +) T cells with CD11a+CC81(+)MyD-1(-) DC was also enhanced by adding IL-1 a lpha, IL-1 beta 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-1 alpha synthesis by this population, which may have important consequences in, vivo.