the most immune-stimulating cells in the human body, occurring naturally in tissues that contact the exterior environment: in the skin and the lining of nose, lungs, stomach, and intestines; they get their name from their long tentacle-like arms, called dendrites, and form from circulating monocytes; they function as antigen-presenting cells and attract invading viruses and bacteria, then cut those proteins into short, linear peptide pieces (see epitope), and carry the fragments on their surfaces (enmeshed in their tentacles) through the blood stream to lymph nodes to activate B cells, helper T cells, and CTLs; only dendritic cells can activate a helper T cell that has never before encountered a particular antigen before.
(see: epitope)