BIO 343 Lecture Notes - Lecture 10: B Cell, Mast Cell, Intestinal Epithelium
Immunology Chapter 10: Systemic vs Mucosal Immune System
Hayden Casassa
• Systemic immune system defends against pathogens penetrating skin
• Mucosal immune system defends against pathogens breaching mucosal surfaces
o Respirator, GI…
o Most bacteria and all viruses gain access to body via mucosal surfaces
o 75% of od’s lphotes ad plasa ells are i seodar lphoid tissues serig uosal
surfaces → and 75% of Abs consist of dimeric IgA secreted by mucosal tissues
• Gastrointestinal Immune System and Gut Commensal Bacteria
o Intestinal Microbiota
▪ Most are commensal bacteria
▪ A balance of right number/ type of bacteria must be maintained
o Benefits of symbiotic relationship
▪ Assist i digestio of ople ars that e a’t digest
▪ Produce vitamins for survival
▪ Limit growth of pathogens by outcompeting for resources
• Commensal bacteria can pose dilemma for immune system (must keep a balance)
o If gut immune system reacts too strong to commensals, the tissues surrounding the intestines
would be in constant state of inflammation
o However, if not dealt with, they would enter bloodstream →even worse life threatening!
• Most bacterial infections of gut tissue are caused by small number of commensals
o Pathogenic variants of commensals arise by acquiring virulence factors that allows them to
breach intestinal epithelium and invade tissue
• GALT and the mucosal immune system
o Tosils, adeoids, appedi, ad Peer’s Pathes
• Microfold (M) cells, transport antigens across epithelial barrier into the lymphoid compartment
o They take antigens into the Peyer’s patches (secondary lymphoid tissue)
• Tonsilitis
o Viral or bacterial infection common in children who are constantly being exposed to new
pathogens
• Appendix
o Secondary lymphoid organ that contains numerous lymphoid follicles
o If severely inflamed it may burst and cause life-threatening peritonitis
• Small intestine is major site of nutrient absorption and surface is deeply folded (SA:V ratio for better
nutrient absorption) and most heavily invested with lymphoid tissue
• Large Intestine (colon)
o Function is reabsorb water and contains the vast majority of commensal bacteria
• Lumen of both sm. And lg. intestine is lined by single layer of epithelial cells coated with mucous
o The mucous is secreted by goblet cells
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Document Summary
Immunology chapter 10: systemic vs mucosal immune system. Intestinal laminia propria where plasma cells, t cells, macrophages, mast cells, eosinophils reside and respond to infection. Inductive compartment: lymphoid area beneath mucosal epithelium where antigens react with dendritic cells and lymphocytes induce adaptive immunity. Inflammation is kept to minimum to avoid damaging gut epithelia: strategies to prevent inflammation in mucosal tissues, regulatory (tregs) and dendritic cells in gut mucosa secrete il-10. Il-10 inhibits inflammatory t cells from making ifn-y. Intestinal macrophages located in laminia propria eliminate pathogens without creating a state of inflammation. L(cid:455)(cid:373)pho(cid:272)(cid:455)tes a(cid:272)ti(cid:448)ated i(cid:374) the pe(cid:455)er"s patches or in the mesenteric lymph nodes return to mucosal tissues as effector cells where they eventually enter the blood. Unlike systemic immune response, effector cells in mucosal system leave mucosal capillaries and populate all mucosal tissues and not just the infected tissue. Mucosal tissues are always populated with activated effector lymphocytes and other leukocytes, even in the absence of infection.
