Tuesday, October 4, 2011

Body's own molecules may repair autoimmunity

By discovering how our body handles protection of ingested food molecules from attacks of the immune system, scientists may very well have found a new way to treat various autoimmune diseases. The production of a molecule called αvß6 made immune cells tolerant towards food particles, while normally all foreign material is being attacked by the immune system. This endogenous system may be used as a foundation for new drugs that combat diseases in which the body is not tolerant towards its own cells and molecules: autoimmunity.

The protein αvß6 is made in the intestines, and works as a barrier for the immune system. It renders dendritic cells, which are in the first line of defence against foreign objects and microbes, tolerogenic: which basically means they fail to develop an immune response against the things that would normally activate them. In this case, it's food molecules, but by administering αvß6 to other parts of the body, immune cells could be made tolerogenic towards other immune response inducing elements. This can be used in autoimmune diseases, where the immune system launches an attack against a specific molecule, that can for example be found on the surface of a specific cell type, causing all these body's own cells to be destroyed by the body itself.

Next to inhibiting dendritic cells, αvß6 was also found to increase the activity of regulatory T lymphocytes. These cells, unlike other T lymphocytes, work as suppressors of the immune system, further showing the role of αvß6 as a promising target to counter autoimmunity. Furthermore, the protein caused inhibition of an immune response dubbed Th2. The immune system balances between an Th1 and Th2 response. The former is used to combat general pathogens such as bacteria and viruses, while a Th2 is predominantly used for making B lymphocytes produce antibodies, but also has a strong association with allergy, which in essence is also a form of autoimmunity.

Th1 and Th2 both have chemical signals associated with them that initiate the immune response. Choosing between a Th1 or a Th2 response is a fine balance that is closely regulated by these so-called cytokines. They induce a Th1 or Th2 response  and consequently inhibit the opposing one. Scientists believe that there may be more than a simple duality, and found evidence for more patterns of immune responses. The immune system is a power hungry mechanism which involves a lot of cells and chemical pathways. The image below shows a bunch of the cells involved with humoral (antibodies that recognize foreign material) and cellular (immune cells tasked with killing pathogens and dysfunctional or infected cells) immunity. The full picture is however much more complex and far from completed. In addition, while scientists have nicely classified every type of immune cell they found, it is now believed that the immune system is much less black and white, and much more plastic, with cell types that can transform themselves and have features that fall into multiple categories.
The discovery of the functions of αvß6 sheds light on a novel mechanism by which the body induces tolerance. A few of these were already found: for example, the tolerance mechanisms that are supposed to prevent that B and T lymphocytes recognize the body's own cells in the first place. When something goes wrong there, however, αvß6 may be used in the future to repair the wrongful attacks of immune cells on the body's own components.

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