Exam 2 - Lecture 20 Flashcards
Lecture 20
The Functions of the Microbiota
*Development of lymphoid organs –Begins is GI tract before birth and matures after being born. Bring-in B cells that secrete IgA.
*Certain bacteria of the microbiota, Bacteroides fragilis and Bacillus subtilisprovide signals.
*Germ-free animals have smaller peyer’spatches, mesenteric lymph nodes, fewer CD4+T cells therefore, less B cells and IgA production.
The Functions of the Microbiota
*Microbiota Signals to the Body -Bacteria, on the skin, respiratory tract, genital tract, or intestine, communicate directly and effectively with their host’s immune system.
*Interaction is essential to the proper functioning of the innate and adaptive immune responses. Alterations or imbalances in the microbiota therefore have profound effects on the functions of the immune system.
*Butyrate and otherssuppress macrophages and promote Treg production, influences goblet cell differentiation and mucus production.
Microbiota do not trigger inflammation in the intestine
*The presence of all these bacterial products has the potential to trigger massive acute inflammation, but this inflammation must not happen unless necessary.
*Balance between proinflammatory Th17 cells and anti-inflammatory Tregcells
*Intestinal helper T cell phenotypes are “plastic,” and precursor cells can differentiate into either Tregor Th17 cells.
*Chemicals produced by the microbiota do not stimulate the dendritic cells (AP) to produce inflammatory cytokines and instead produce IL-10 down regulating inflammation with FoxP3+ Tregs .
Hygiene Hypothesis
*Lack of early childhood exposure to infectious agents, symbiotic microorganisms (gut flora, probiotics) and parasites increases susceptibility to allergic diseases by suppressing the natural development of the immune system (Wikipedia).
*Joni Mitchell in song Big Yellow Taxi -Paved paradise and Put-up a Parking Lot –“give me spots on my apples and leave me the birds and the bees, please”.
Hygiene Hypothesis and Dysbiosis
*Preventing or eliminating an animal’s exposure and colonization of bacteria into its microbiome causes dysbiosis:
*Antibiotic treatment is an important cause of dysbiosis. This can radically alter the composition of the intestinal microbiota and increase the risk of developing infections with organisms such asClostridium difficileor overgrowth with other unwanted pathogens.
*Equine laminitis –limited ability to digest starch in small intestine. Get overspill to hind gut, where starch is instead fermented releasing toxins into the blood stream which inflame the capillaries of the lamina.
*Rumen acidosis –similar scenario with over ingestion of carbohydrate rich foods causing leakage of bacteria across gut lining causing systemic inflammation
Hygiene Hypothesis and Dysbiosis
*Equine laminitis –limited ability to digest starch in small intestine. Get overspill to hind gut, where starch is instead fermented releasing toxins into the blood stream which inflame the capillaries of the lamina.
*The microbiota of healthy horses has been compared with those suffering from laminitis with significant taxonomic differences. The relative abundance of Firmicutes decreased (69.21%, healthy horses and 56.72%, laminitichorses), and the relative abundance of Verrucomicrobiaincreased (18.13%, healthy horses and 27.63%, laminitichorses) (Steelman et al., 2012).
*Acid-intolerant obligate fibrolyticbacteria died off in large numbers, possibly triggering a release of endotoxins and exotoxins, which have been associated with hindgut epithelial cell damage and increased intestinal permeability (Goer, 2010).
*Rumen acidosis –Feeding of rapidly digestible carbohydrates (grains) when fermented increases and eventually can over produce D-lactate causing pH to drop.
*Reduces richness of microbiota and can cause switch in bacteria that can invade epithelial cells and cause inflammation.
Hygiene Hypothesis and Dysbiosis - IBD in Pets
*Inflammatory bowel disease in dogs
*presents with a history of chronic vomiting, diarrhea, and weight loss.
*Breed predisposition in Weimaraners, Rottweilers, German Shepherds, Border Collies, and Boxers.
*The most common form is a lymphocytic-plasmacyticenteritis.
*Increase in Th17 cells –pro-inflammatory
*Patients demonstrating mild symptoms of the disease are usually placed on an appropriate diet which may be combined with immunomodulativeor probiotic treatment.
*Additionally, are given fiber(canned pumpkin) to help with diarrhea. Sick animals crave fiber. Also given commercial restorative supplements, such as Fortiflorathat contain a guaranteed amountof beneficial microorganisms.
