Differences in cytokine synthesis by the sub-populations of dendritic cells from afferent lymph

Two phenotypically distinct subpopulations of dendritic cells (SIRPalpha+ CC81Ag- DC and SIRPalpha- CC81Ag+ DC) have previously been identified in bovine afferent lymph which show functional differences when assayed in vitro. The purpose of this study was to investigate whether differences in cytokine production between the two subpopulations might occur which could influence the bias of the immune response they stimulate. Qualitative and quantitative polymerase chain reactions were used to detect specific mRNA transcripts and flow cytometry and enzyme-linked immunosorbent assays were used to detect protein production. The SIRPalpha- CC81Ag+ DC produced considerably more interleukin-12 (IL-12) mRNA transcripts and protein than the SIRPalpha+ CC81Ag- DC. Conversely, SIRPalpha+ CC81Ag- DC contained more of both transcripts and protein for IL-1 and of transcripts for IL-6. A small percentage of both subpopulations produced interferon-gamma (IFN-gamma) as evidenced by cytoplasmic staining. Stimulation of DC by culture with CD40L+ cells increased the production of IL-1, IL-6 and IL-12 but quantitative differences between the subpopulations remained. Production of IL-10 was also evident following culture with CD40L+ cells or lipopolysaccharide primarily by the SIRPalpha+ CC81Ag- DC. No evidence was found for type 1 IFN production, and hence plasmacytoid DC, by DC in afferent lymph; both subpopulations appear to be myeloid in origin. These different cytokine repertoires of the two subpopulations of ex vivo DC isolated from afferent lymph imply functional differences that could influence the presentation of antigen to T cells and bias of the immune response following vaccination or infection.