Intestinal immunity

Microorganisms that inhabit the intestinal tract is ref2242ed to as the intestinal microbiome

Intestinal intraluminal bacteria affect the development of the intestinal immune system, supplied a key nutrients and modulate energy metabolism.

Intestinal microbacteria are acquired at birth and change rapidly during the first year of life.

The fecal bacterial population in adults is relatively stable over time, but fluctuations may result from environmental, developmental and acquired disease factors.

The interaction between the host, and bacteria can be mutually beneficial or adverse and incite intestinal inflammation.

Bacteria that adhere to the intestinal mucosal may be particularly important in creating inflammatory changes in the bowel.

Microbial antigens normally present in the intestinal lumen are apparently capable of creating inflammation in the gut.

Patients with ulcerative colitis and Crohn’s disease have depleted and reduced diversity of mucosal associated Firmicutes and Bacteroidetes compared to controlled subjects.

The intestinal epithelium plays a significant role in shaping the mucosal immune response as it is the interface between intestinal bacteria and lymphoid tissue of the gastrointestinal tract.

Intercellular junctions maintain an intact epithelial mucosal barrier by sealing the space between adjacent epithelial cells.

When the regulation of tight junctions is impaired and the para-cellular space has increased permeability inflammatory bowel disease may result.

Defective intracellular junctions may be due to a defect in the area function or may be a result of inflammation.

Defenses against bacterial invasion also comes from specialized epithelial cells, including Paneth cells and Goblet cells.

Goblet cells regulate mucus production and other factors that contribute to epithelial repair and regulation of inflammation.

Paneth cells secrete antimicrobial peptides.

Alpha-defensins are anti-microbial peptides produced by Paneth cells.

Intestinal mucus limits contact between bacteria and epithelial cells which line the intestine.

Intestinal epithelial regeneration and repair help to control and resolve inflammatory responses that occur with injury.

The intestinal lamina propria contains immune cells that balance immune tolerance of luminal bacteria with the need to defend against pathogens and the excessive entry of bacteria.

In the presence of inflammatory bowel disease, inflammatory responses promote epithelial injury, which results in erosion formation, ulcerations and decreased production of defensin.

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