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Dendritic cells are a part of the immune system that plays a significant role in the defense of the body. The cells naturally eat up invaders, and then display bits of the invader on the outside of the cells. This allows the body to identify characteristic pieces of an invader and prepare for later invasion by the same pathogen. Scientists think that they can harness this natural cell mechanism and use it in the treatment of cancer as a technique called dendritic cell immunotherapy. As of 2011, the scientists see potential to use the dendritic cells to display pieces of tumors, so that the immune system can target the tumor cells for destruction.
Since their discovery in the latter half of the 20th century, dendritic cells, and the way in which they work, have been under study by scientists. The name comes from their appearance under the microscope, as the cells have many branches, like a tree. In Greek, dendron means tree. These cells are found in areas of the body that are the first lines of defense against infection, like the skin, and they are also located in parts of the body that are heavily involved in the immune response, such as the lymph nodes and spleen.
When a dendritic cell comes across an invader, the cell eats up the invader and breaks it down into fragments. The fragments that are potentially useful as identifying marks for the immune system, such as the molecules present on the outside of the invader, are displayed on the outside of the dendritic cell. After the cell is exposed to this invader, it moves to the lymph nodes and spleen, as these are the parts of the body that act as a base for the immune response cells to interact. The visible molecules on the outside of the dendritic cell then act as signals to the other immune cells present in the spleen or lymph node to produce a specific response to this particular invader.
Tumor cells are not infectious agents like viruses or bacteria, but they are undesirable cells. Normally, a dendritic cell does not kill, eat and display bits of tumor cell on its outside. This is because tumor cells originally come from a mutated normal cell of the body, which the dendritic cell does not recognize as an invader. Tumors also do not produce sufficiently abnormal molecules for the immune system to recognize and destroy them. Dendritic cell immunotherapy, however, is a technique that brings the tumor cells to the attention of the immune system.
In laboratory conditions, the dendritic cells are mixed up with molecules that are specific to a particular tumor. In the laboratory, the dendritic cells recognize the tumor molecules and display them on the outside of their cells. Once the cells are injected into the body of the patient, the dendritic cell immunotherapy effect can potentially alert the immune system to the threat from the tumor cells. As of 2011, approaches to cancer therapy in the dendritic cell immunotherapy field are still under research. Although the field has hypothetical potential in cancer therapy, the efficacy of treatment using this technique is unknown as of 2011.
On April 29, 2010, the FDA approved Provenge, an immunotherapy from Dendreon Corp. The approval was based on a 4.1 month life extension from three phase III trials. Further post hoc analysis has indicated a 13 month extension if the PSA baseline was < 22ng/ml at the start of treatment. Although not a cure, the life extension in this patient group is not inconsequential.
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