Definition, figure and function:
Dendritic cells belong to the defense cells of the immune system of mammals. The name has nothing to do with the cell processes of nerve cells (dendrites), but derives from the characteristic-branched structure of the dendritic (from the ancient Greek 'dendron' = tree) cells. In the 19th century, the pathologist described Paul Langerhans the cell type for the first time, but erroneously assumed that the dendritic cells belong to the nerve cells. Therein lies the name similarity of both cell types.
Dendritic cells develop from monocytes and can be found in almost all body tissues, especially in the gastrointestinal tract, the lungs, and the mucous membranes of the mouth and nose.
The central task of dendritic cells is the antigen production and antigen presentation in the context of the innate immune reaction. The process looks like this:
1. A dendritic cell in the tissue phagocytoses a foreign pathogen. Phagocytosis can occur only once for each dendritic cell. At this point, the cell is still in the immature state.
2. The dendritic cell now leaves the tissue and 'wanders' (cell migration) to the nearest lymph node.
3. Antigens of the previously phagocytised pathogen are transferred from the dendritic cell to the cell surface (antigen production) and visualized for T lymphocytes (antigen presentation).
4. With the presentation of the proteins, the antigen-presenting cell moves into the mature state.
5. Chemokines (chemotactic cytokines) released by the dendritic cells activate the T lymphocytes from the immediate environment.
6. The attracted T lymphocytes recognize and bind to the antigens presented.
7. The T cell receptor is now able to recognize the specific antigens previously presented by the dendritic cell.