CD2 distinguishes two subsets of human plasmacytoid dendritic cells with distinct phenotype and functions

Plasmacytoid dendritic cells (pDCs) are key regulators of anti-viral immunity. They rapidly secrete IFN-alpha and cross-present viral antigens thereby launching adaptive immunity. Here we show that activated human pDCs inhibit replication of cancer cells, and kill them in a contact dependent fashion. Expression of CD2 distinguishes two pDC subsets with distinct phenotype and function. Both subsets secrete IFN-alpha and express Granzyme B and TRAIL. CD2high pDCs uniquely express lysozyme and can be found in tonsils and in tumors. Both subsets launch recall T cell response. However, CD2high pDCs secrete higher levels of IL12 p40, express higher levels of co-stimulatory molecule CD80 and are more efficient in triggering proliferation of naïve allogeneic T cells. Thus, human blood pDCs are composed of subsets with specific phenotype and functions. pDC subsets were isolated from two different donors. They were analyzed in two independent experiments.