Dendritic cells, sometimes referred to as DC, are part of the mammalian immune system. In humans and other mammals, these cells are found in tissues and organs that frequently come in contact with the exterior environment or external substances. Such tissues and organs include the skin, stomach, nose, lungs, and other digestive organs, although DC formation initially takes place in progenitor cells in the bone marrow.
As part of the human immune system, dendritic cells act as a communication vehicle between multiple key cells. They function in tandem with macrophages and lymphocytes to transport antigens, which are molecules that trigger an immune response. The branched dendritic structure includes a threadlike tentacles that capture antigens in order to present them to T cells. The T cells, also known as white blood cells, then initiate a defensive immune response. This process allows the mammalian immune system to adapt to biological attacks on the body's cells.
Depending on their type and origin, dendritic cells possess a relatively short life span of only days from their initial formation. When in their immature stage, they can remain dormant for an indefinite period of time. Repeated contact with pathogens in the body can trigger cell maturation, at which point the the cells become active antigen carriers.
Diseases such as HIV/AIDS make use of the antigen transport process to infect and cripple the immune system. By attaching itself to dendritic cells, the HIV virus can then spread to helper T cells, disable them, and even use them to replicate. This subjugation of the autoimmune response has presented problems in treating HIV infections.
While HIV may use antigen transport to further infect its host, researchers have experimented with using dendritic cells to prevent, treat, and possibly cure cancer via immunotherapy. This therapy involves creating vaccines from cancerous tumor cells. To accomplish this, the tumor cells are bonded to the dendritic cells, which then present the cancer to T cells. In some patients, this treatment has produced a successful antigen response that resulted in patient remission. In other patients, T cells provided no response to the presence of the vaccine.
In mammals other than humans, DCs may exhibit more unique behaviors. In addition to triggering autoimmune response, they may also take a more active role in immune defense, depending on their environment. The behavior of the cells is often dependent on the animal, its specific physiology, and its particular method of immune response.