Question

Describe the urinary system’s defenses against pathogens

Answer 1

Ans.The urinary tract is constantly exposed to microorganisms that inhabit the gastrointestinal tract, but generally the urinary tract resists infection by gut microorganisms.

Protection from microbial organization is mediated by various soluble factors that are secreted into urine and by anatomical barriers such as glycoproteins plaque uroplakins and a layer of hydrated mucus.

• In addition, urinary tract is lined by epithelial cells and various resident immune cells that further protect against infection. The epithelial cells lining the urinary tract are the first line of defence against pathogens. These cells secrete a plethora of soluble compounds ranging from pro-inflammatory cytokines to antibacterial agents
• Neutrophils are the first immune cells to be recruited to the bladder following UTIs, and they have a predominant role in bacterial clearance.
• A substantial population of macrophages resides in the submucosa of the urinary tract, and more cells are recruited to these sites following infection37. Upon activation, these macrophages produce crucial cytokines and chemokines.
• Mast cells are another resident immune cell type located underneath the uroepithelium in close proximity to blood and lymphatic vessels that traverse the mucosal region . In the bladder, mast cells are also found in high numbers in the detrusor muscle region42. Mast cells have a pivotal sentinel and key immunomodulatory role during UTIs, which is partly due to their ability to release many pre-stored pro-inflammatory mediators — such as TNF, histamine and several chemokines — upon activation43.

These barriers prevent pathogens from entering urinary tract and from establishing persistent infection.