The Role of CD4+ T Cell Subsets in the Mechanism of Action of Vedolizumab in Ulcerative Colitis

The cause of Inflammatory Bowl Disease (IBD) is not known, but studies from patients with IBD have found that these patients make unusually strong immune responses to their own intestinal tissues and to bacteria that normally live in the healthy gut. These overactive immune responses might result from an imbalance of T-lymphocytes, which are a type of white blood cell that recognize and respond to threats like infection or damaged tissues. In healthy tissues, a type of T-lymphocytes called T-regulatory cells control excess inflammation by preventing other T cells, called T-effector cells from responding. We believe that T-regulatory cells are somehow less active in IBD, resulting in damage to intestinal tissues by the T-effector cells. T-lymphocytes, including both T-regulatory and T-effector cells, are guided to different parts of the body by 'alpha4beta7-integrin' molecules. Vedolizumab or Entyvio works by blocking this homing molecule so that T cells do not reach the intestine, but stay in the blood where they cannot aggravate your IBD. This study will help in understanding how Vedolizumab helps to heal or decrease the symptoms of your Ulcerative Colitis. The effect of Vedolizumab on different types of T cells in the human intestine has not yet been studied. However, the investigators think that Vedolizumab will shift the balance of T cells in the intestine towards more healing T-regulatory cells and less damaging T-effector cells. The purpose of this study is to measure the different types of T cells in participants' blood and intestinal tissue before and during Vedolizumab treatment.