Leukemic plasmacytoid dendritic cells share phenotypic and functional features with their normal counterparts

This work aims to further characterize the newly described leukemic plasmacytoid dendritic cells (LPDC), for which we had previously demonstrated their normal, PDC‐like ability to produce IFN‐α. In addition, LPDC also express the specific antigens BDCA‐2 and BDCA‐4. Importantly, they become fully competent antigen‐presenting cells (APC) after a short maturation induced by IL‐3 + CD40L or virus, exhibiting a characteristic APC phenotype (high expression of CD83 and of the costimulatory molecules CD40, CD80, CD86). Whereas IL‐3 + CD40L‐activated LPDC prime naive CD4+ T cells towards a Th2 pathway (IL‐4‐secreting T cells), virus‐activated LPDC drive a Th1 profile (IFN‐γ–secreting T cells). Moreover, we show in one case that LPDC are able to capture, process and present exogenous antigens, leading to the activation of both CD4+ and CD8+ T cell clones in an antigen‐specific manner. This study further characterizes the phenotype and immunological functions of LPDC.