These lecture notes on Inflammatory Bowel Disease (IBD) provide a comprehensive overview of the pathophysiology, clinical presentation, and treatment strategies for IBD, including Crohn’s disease and ulcerative colitis. The notes cover the immune system’s role in disease progression, key molecu...
L2 Inflammatory Bowel Disease
Learning Objectives:
1. Recognize the main components of the gut mucosal immune system.
2. Summarize the molecular controls of T cell migration to the gut.
3. Identify the several epithelial cell types that are present intestinal epithelium.
4. Understand the importance of gut microbiota in health and disease.
Examples of mucosal tissues of the human body: urogenital tract, gastrointestinal tract and
respiratory tract
Systemic vs Mucosal Environment:
Systemic: Contained, sterile, encounters antigens rarely
Most immune cells in the mucosal immune system are found in the gut. Examples of
conventional immune cells include dendritic cells, macrophages, neutrophils, mast cells,
eosinophils, basophils, T cells and B cells
Some more specfic cells can be found in the mucosal immune system as they are found in
higher proportions and these include epithelial cells, M cells (found in Peyer’s patch which are
important when presenting antigens to other cells) , IntraEpithelial Lymphocytes (IEL)
CD8αα+ T cell or γδ T cell and innate lymphoid cells
Intestinal T-cells
- CD4+ T cells found mostly in Peyer’s patch
- CD4+ T cells found mostly in Lamina propria (which is the area below the Peyer’s Patch)
, - IntraEpithelial Lymphocytes (IEL) have CD8αα+ T cell or γδ T cell (γδ T cell express
gamma and delta chain rather than alpha and beta chain)
2. Summarize the molecular controls of T cell migration to the gut.
1. T-cells enter Peyer’s patches from blood vessels directed by homing receptors CCR7 and L-selectin
2. The T-cells encounter the antigens that are transported by M cells; M cells can present cells from the
lumen to dendritic cells and these dendritic cells present those antigens to the T-cells and activates
them.
3. Ativated T-cells drain via mesenteric lymph nodes (lymph nodes found in the gut) to the thoracic duct
and the T-cells then return to the gut via the bloodstream
4. The activated T-cells express homing receptors (receptors that will direct them to the gut) such as
alpha-4:beta-7 integrin and CCR9 home to the lamina propria and intestinal epithelium of small
intestine
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