Abstract
Peripheral blood contains two major particular infrequent dendritic cells (DC) subsets linking the innate and specific immune system, the myeloid DC and plasmacytoid DC equivalent to the natural interferon-producing cells (NIPC). The functional characterization of these cells demands large volumes of blood, making a large animal model more appropriate and beneficial for certain studies. Here, two subsets of porcine blood mononuclear cells expressing swine workshop cluster 3 (SWC3, a SIRP family member), are described and compared to monocytes. The blood DC specialized in T-cell stimulation were major histocompatibility complex (MHC) class II+, CD80/86+, CD1+/-, CD4-, and in contrast to monocytes CD14-. A CD16- and a CD16+ subset could be discriminated. Granulocyte-macrophage colony-stimulating factor and interleukin-3 were survival factors for this DC subset, and culture induced an up-regulation of MHC class II and CD80/86. The second subset described, are porcine NIPC, typically CD4++, MHC class IIlow, CD80/86low, CD1-, CD8-/low, CD16-/low and CD45RA-/low. Porcine NIPC had high interleukin-3 binding capacity, and survived in response to this cytokine. Their unique function was strong interferon type I secretion after virus stimulation. Both subsets were endocytically active when freshly isolated, and down-regulated this activity after in vitro maturation. Taken together, the present report has delineated porcine blood DC and NIPC, permitting a more detailed understanding of innate immune defences, particularly in response to infections.