Co-ordination of Incoming and Outgoing Traffic in Antigen-Presenting Cells by Pattern Recognition Receptors and T Cells

Dendritic cells are innate sentinels of the immune system and potent activators of naive T cells. Mechanisms must exist to enable these cells to achieve maximal activation of T cells specific for microbial antigens, while avoiding activation of T cells specific for self-antigens. Here we discuss how a combination of signals from pattern recognition receptors and T cells co-ordinates subcellular trafficking of antigen with both major histocompatibility complex class I and class II molecules and T-cell costimulatory molecules, resulting in the preferential presentation of microbial peptides within a stimulatory context.