The appendix in intestinal immunity and inflammatory bowel disease

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Inflammatory bowel diseases (IBD) consist of two entities: ulcerative colitis and Crohn's disease. IBD causes relapsing and remitting gut inflammation in relatively young populations of patients. Our understanding of causes of IBD is poor, but the diseases involve an interaction between the intestinal immune system, genetic predisposition and bacteria in the gut. One unexplained observation, made by a number of groups, is that removal of the appendix, especially if performed when young, protects against the later development of ulcerative colitis and probably Crohn s disease. If IBD does develop following earlier appendicectomy, it tends to be less severe. In this project, we plan to examine the immune features of the appendix, in human and mouse. The appendix is a major source of immune cells in the intestine but the nature of these cells and their functions are poorly understood. The aims of the project will explore the nature of immune cells, known as T lymphocytes, isolated from human and mouse appendices. Changes with age will be examined, to explain the age-related nature of the appendicectomy-IBD link. Anti- and pro-inflammatory characteristics of the cells will be studied, the migration pathways of these cells from appendix to other parts of the intestine will be clarified, and the therapeutic potential of these T cells in a mouse model of IBD will be elucidated. In addition, this will be the first study to develop and analyse a mouse model of appendicitis, which is very poorly understood. These studies will make important observations relevant not only to IBD, but to the immune function of the intestine, with implications for our fundamental understanding of the way we are protected from our hostile environment.