Flow cytometry based analysis for subsets of Plasmacytoid Dendritic Cells (pDC) from human PBMC (100.31)

Dendritic cells are a heterogeneous group of antigen presenting cells that link innate and adaptive immunity. In mice and humans, subsets of DC have been identified, based on origin, location, differentiation, phenotype and functions. Newly identified markers, availability of mAb(s) and advanced flow-cytometry techniques have helped in enumerating existence of such subsets. Plasmacytoid dendritic cells (pDC) are peripheral blood DC subsets, which produce IFN (Type I) and are vital for anti-viral immunity. pDC exist in small numbers (~0.1-0.5%) in peripheral blood and their phenotype analysis by flow, includes CD123 and HLADR expression on lineage negative populations of PBMC. Recently, pDC were shown to play important roles (besides anti-viral) in other human diseases such as lupus and psoriasis but it is not known if distinct subsets are associated. In the present study we used three markers viz. CD123, BDCA-2 and ILT7 (newly identified) to analyze potential subsets of pDC. As Type I IFN producers, pDC express intracellular toll-like receptors TLR7 and TLR9 and our analysis extends to include whether these subsets differ in TLR expression, particularly focusing on TLRs playing an important role in innate-IFN (Type I) production. In order to understand the role of pDC (subsets) in induction of anti-immune responses towards other microbes, expression of non-specific markers such as Dectin-2 and TLR 10 were also tested using newly available mAb(s).