27 February 2008

Dendritic Cells in IBD Pathogenesis

After reading "Translational Research in Inflammatory Bowel Disease" the role of dendritic cells in pathogenesis of IBD interested me. A little info : All dendritic cells are derived from bone marrow progenitor cells and once differentiated, are termed "immature" dentritic cells. These immature cells constantly "sample" their environement for viruses, bacteria, and other pathogens via high endocytotic ability. Toll-like receptors are prevalent on the immature cell surface and bind to highly conserved chemical signatures on pathogens as a part of innate immunity (i.e. passed on genetically). Once the toll like receptor binds to its particular ligand, the immature dendritic cell becomes activated into a mature dendritic cell and phagocytosizes the pathogen. They upregulate cell surface receptors that act to activate T-cells such as CD80, CD86, and CD40. Dendritic cells release powerful cytokines as well as high levels of TNF alpha and the anti-inflammatory cytokine IL-10, both of which begin and escale the inflammatory response, which is the main factor in IBD.
Dendritic cells then move to lymphatic tissue in the spleen or lymph nodes via blood and it is here that ingested pathogen is broken down and some of its protein sequences are expressed on the surface. The antigen is presented to and activates helper T cells, killer T cells, and B-cells, which in turn create antibodies to continue the immune response. This is a likely starting point in the pathogenesis of IBD, as the main problem is an abnormal initial immune response to normal gut flora. Toll like receptors, which are genetically encoded, may play a large role in IBD as they are the first point at which a normal pathogen is seen by the immunity as foreign and as cause for an inflammatory response.
The article speaks about a possible "IBD chip" in the near future, where an individual can be genetically screened and possible mutant toll like receptor genes, or other IBD related genes can be pin pointed and perhaps small molecules or anitbodies can be used to antagonize the abnormal immune response. This is very interesting and t seems to me that this would be the best point to begin in fighting IBD, at its root.

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