Malignant counterpart of myeloid dendritic cell (DC) belonging to acute myelogenous leukemia (AML) exhibits a dichotomous immunoregulatory potential

Dendritic cells (DCs) play a central role in immune regulation. Some leukemic cells are argued to be malignant counterparts of DC because of their ability to differentiate into leukemic DC. We characterize DC-like leukemia homogenously expressing CD11c+CD86+ in acute myelogenous leukemia patients. They express the Wilms' tumor-1 antigen and common DC phenotypes (i.e., fascin+, CD83+, and DR+) directly. Purified leukemic cells produce interleukin-12 (IL-12) simultaneously with Fas ligand (FasL) and IL-6, which may suppress T cell-mediated immunity. These cells can elicit strong allogeneic T cell responses as well as induce tumor-specific CD8+ cytotoxic T cells, suggesting that they effectively present tumor-associated antigens. In contrast, they drive primary T cells toward apoptosis mediated in a tumor-specific way by a Fas-FasL interaction. Taken together, DC-like leukemia uniquely influences immune surveillance in contradictory ways, some of which may be involved in the mechanism of immune escape.