Acquisition and presentation of tumor antigens by dendritic cells.

Dendritic cells (DCs) are master regulators of the immune response and, because of their peculiar features in antigen acquisition, processing, and presentation, they play a critical role in activating an efficient antigenspecific T-lymphocyte response against tumors. However, the DC family is composed of different cell subsets, which may differently contribute to tumor-specific T-cell activation. In addition to the DC subset involved, the induction of a tumor-specific adaptive immune response is also dependent on DC interactions with other innate cell effectors, such as natural killer cells. The different modalities by which DCs can acquire tumor antigens also significantly affect antigen presentation because, in addition to the presentation of tumor antigens on MHC class II upon the classical exogenous antigen processing pathway, DCs are equipped to directly activate cytotoxic T cells via both cross-priming and cross-dressing. Here, the different forms of tumor antigen presentation by DCs are reviewed and discussed. We also discuss the ways in which this novel information could be exploited in the design of DC-based cancer vaccines.