Isolation of human blood DC subtypes

Human blood dendritic cells (DCs) are a rare, heterogeneous cell population that comprise approximately 1% of circulating peripheral blood mononuclear cells (PBMCs). Their isolation has been confounded by their scarcity and lack of distinguishing markers and their characterisation perplexed by the recent discovery of phenotypic and functionally distinct subsets. Human blood DCs are broadly defined as leukocytes that are HLA-DR positive and lack expression of markers specific for T cell, B cell, NK cell, monocyte and granulocyte lineages. They can be subdivided into the CD11c(-) (CD123(+)CD303(+)CD304(+)) plasmacytoid DC and CD11c(+) myeloid DC, which can be further subdivided into three subsets based on differential expression of CD1c, CD141 and CD16. DC can be isolated from peripheral blood by using an initial density gradient centrifugation step to enrich for mononuclear cells followed by immunomagnetic depletion of cells expressing markers specific for leukocyte lineages and undesired DC subsets. Subsequent flow cytometry-based cell sorting allows the isolation of highly pure individual DC subsets that can then be used for functional studies.