Dendritic cell

A dendritic cell is a white blood cell named for the long, branching projections that reach out from its surface, like the dendrites of a nerve cell. Dendritic cells come from bone marrow precursors and wait in tissues that meet the outside world, such as the skin, where a type called the Langerhans cell lives, and the linings of the airways and gut. They belong to the innate immune system but are its main link to adaptive immunity.

In the tissues, an immature dendritic cell keeps sampling its surroundings, taking in microbes and debris by phagocytosis and other forms of uptake. Sensors such as toll-like receptors tell it when the material is dangerous. The cell then cuts the proteins into short peptides, loads them onto MHC class II and class I molecules, and moves through lymphatic vessels to the nearest lymph node. There it shows the peptides to naive T cells, together with the extra signals needed to switch them on. This makes dendritic cells the most powerful antigen-presenting cells for starting a new T-cell response.

Ralph Steinman, who identified the cells in the 1970s, shared the 2011 Nobel Prize in Physiology or Medicine for the discovery. Dendritic cells are also being tested in cancer vaccines that train them to present tumor antigens.