Plasmacytoid dendritic cell subpopulations in head and neck squamous cell carcinoma

Human plasmacytoid dendritic cells (PDCs) are present in solid tumor tissue and metastatic cervical lymph nodes (CLN) in head and neck squamous cell carcinoma (HNSCC). We recently showed that classical PDC functions are heavily disturbed in the tumor microenvironment. In this study we present a new approach to the subject by introducing 3 PDC subsets in HNSCC, characterized by the surface markers CD25, CD56 and CD203c. The first subset, positive for CD25, is significantly induced by HNSCC in vitro and present in metastatic lymph nodes in vivo. This subset can be phenotypically subdivided into matured cells and into a group expressing early T cell markers. Functionally this subgroup is associated with the secretion of IL-8. The second subset, positive for CD56, constitutes 4-5% of all PDCs and is significantly down-regulated by HNSCC. Furthermore, this population sporadically expresses perforin/granzyme B and is absent in metastatic lymph nodes. The third subset, positive for the basophile marker CD203c, is inducible by crosslinking BDCA-2 in the presence of HNSCC and IL-4. Future studies will have to clarify the in vivo relevance of the different PDC subsets in HNSCC.