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Digestive System Ulcerative Colitis What causes UC?
What causes UC?
About Ulcerative Colitis

What causes UC?

Ulcerative colitis is believed to be an autoimmune condition. Your immune system is your body’s defence against infection. Normally, your immune system is capable of distinguishing between potentially harmful germs and other cells within your own body. However, if you have an autoimmune condition, the immune system becomes confused and attacks your own healthy tissues. 

The most popular theory as to why this happens in ulcerative colitis is that your immune system mistakes harmless bacteria within the colon as a threat and attacks the tissues in the colon. The immune system releases an enzyme called TNF-alpha, along with other cells. See the diagram below for an explanation of TNF-alpha.

An infographic with four statements about TNF alpha. TNF is a cell of the immune system known as a cytokine, and can have multiple effects of most cells in our bodies, it plays a big role in regulating our bodies’ inflammation response, it is also a key player in the action (or pathogenesis) of many inflammatory and autoimmune diseases, including UC and The exact effects vary based on disease type.

The release of TNF begins an immune response. This leads to the accumulation of yet more cells, as explained below.1

A diagram with schematic images of three immune cells - macrophages, neutrophils and intestinal fibroblasts. The diagram states that the immune response begins with the body producing more immune cells than usual, causing the accumulation of macrophages (which produce more cells which encourage the breakdown of the intestine), neutrophils (which release a protein (enzyme) which causes breakdown of the matrix) and intestinal fibroblasts (which form structures in the intestine).

This causes the colon to become inflamed. Experts are unsure exactly what causes the immune system to behave in this way, although many experts believe that it is a result of both genetic and environmental factors. 

References

  1. I. Ordás, L. Eckmann, M. Talamini, D. C. Baumgart, W. J. Sandborn. Ulcerative colitis: seminar. The Lancet. 2012;308(9853)1606-1619.