Immune Activation: Death, Danger and Dendritic Cells Bali Pulendran  Current Biology  Volume 14, Issue 1, Pages R30-R32 (January 2004) DOI: 10.1016/j.cub.2003.12.020

Figure 1 Dendritic cells as immune sensors of life, death and danger. Dendritic cells express many different receptors, including Toll like receptors (TLRs), which enable them to sense life (bacteria, viruses, parasites, fungi etc) and death (uric acid crystals and gp96 and hsp70 from necrotic cells, apoptotic bodies, etc). Many signals of life and death can harm the integrity of the local tissues and of the host itself – thus these constitute clear danger signals for the host. Dendritic cells rapidly become activated in response to such signals, and result in immune activation and inflammation. It is tempting to speculate that other manifestations of danger that activate immune responses may include signals such as neurotransmitters released during the fight–flight response, or severe cell death caused by other trauma, cardiac arrests, or strokes. In contrast, ‘quietly’ dying apoptotic cells or other undefined signals that represent no harm to the integrity of the host may not activate dendritic cells or immune responses and may lead to immune quiescence or tolerance. Current Biology 2004 14, R30-R32DOI: (10.1016/j.cub.2003.12.020)