Intracellular mechanisms of antigen cross presentation in dendritic cells.

The induction of most CD8+ T cell responses by dendritic cells (DCs) requires the presentation of peptides from internalized antigen by class I MHC molecules. Increasing number of reports have shown that cross presentation is involved in transplant rejection, in immune responses to viral infections, in certain autoimmune diseases and cancer. The precise role of cross presentation in the initiation of immune responses in vivo, however, remains a matter of debate. This ongoing controversy is, at least in part, due to a lack of understanding of the molecular machinery that determine cross presentation pathways in terms of cell biology. The present review aims to summarize recent insights and advances that help enlighten the intracellular steps of antigen cross presentation in DCs.