Flashcards in Special Lecture: Mucosal Immunology Deck (21):
The immune system is "not aware" of the microbe, because of physical separation
IgA binds to the microbe and keeps it away from immune cells.
keep bacteria away from immune tissue
Region of epithelial cells close to the immunological tissue. We don't want symbiotic microbes here.
What role do goblet cells play in immunity?
Goblet cells generate mucous to keep microbes from immunological tissue.
What role does IgA play in mucosal immunity?
IgA is the dominant form of immunoglobulin. It is found in the mucus, tears, saliva, and breast milk. IgA is a major factor involved in host-microbe dialogue at mucosal sites
IgA at epithelial surfaces
IgA binds to toxins, and pathogens in the GI tract.
recognize LPS; lowered expression in healthy IEC; slightly elevated in IEC that have not yet migrated up the villi; limited availability of co-receptors MD-2, CD14 and LPS-binding protein (LBP)
recognizes flagellin; only expressed basolaterally
recognizes dsRNA; expressed immediately beneath the luminal surface
recognizes unmethylated bacterial DNA; basolateral TLR9 activation elicits a classic inflammatory response whereas apical TLR9 attenuates that response
CD8+ or CD4+; Involved in inhibition or activation depending on what they encounter.
CD4-CD8-ab or CD4-CD8-gd
Microfold cells - naked areas in the epithelial cells not covered by mucous, that take up antigen, present to APCs; Dendritic cells can also extend through the epithelium and sample for antigen.
Clearance of extracellular pathogens (Klebsiella, Citrobacter, fungi) via neutrophil recruitment ;plays a role in Tissue inflammation; Immunopathology & autoimmunity
Healthy (Probiotic) Microbes
Lactobacillus spp; Bifidobacterium spp; Faecalibacterium prauznitsii
Colitogenic (Disease causing) microbes
Klebsiella pneumoniae; Proteus mirabilis; Adherent and invasive E. coli; Helicobacter spp.
What microbial family is important in CD4 T reg development?
Clostridium is FOXP3 producing.
What microbe promotes the formation of Th17?
SFB; Segmented Filamentous Bacteria.
What are some of the functions of gut bacteria?
1) Extracting nutrients from food 2) competitive exclusion of pathogens 3) Epithelial cell maturation 4) lymphocyte development 5) immune regulation/homeostasis 6) overcoming dietary restrictions (degrading dietary polysaccharides)