IMMUNOLOGY OF THE GUT Flashcards
Outline the organisation of the intestinal flora as you move further down the gut?
the concentration of bacteria incresses and the more anaerobic the bacterua become
whats the function of the intestinal flora?
produce vitamins
digest food components that we cant
mounts protective immune responses
whats the most predominant cell in the small intestine?
enterocytes
whats the most predominant cell in the large intestine?
colonocytes
outline the differences in intestinal epithelium in small vs large intestine?
small has enterocytes and large colonocytes
small has paneth cells and large does not
small has villi whereas large does not
large insteastine also doesnt have plicae circularis like the small intestine
what is goblet cells’ function in the epithelium of the small and large intestine?
secrete mucins (high molecular weight glycoproteins) to form the mucus layer
whats the function of Paneth cells?
to secrete antimicrobial peptides
what are the lymph nodes found all around the GIT?
mesenteric lymph nodes
what are the 3 subsets of CD4+ Th cells?
effector subsets and regulatory subsets and follicular helper cells
what are the effector CD4+ Th cells?
Th1
Th2
Th17
what are the regulatory CD4+ Th cells?
Tr1 Th3 CD25+
what cytokines do Th1 release?
IFN gamma
what cytokines do Th2 release?
IL=4 IL-5
what cytokines do Th17 release?
IL-17
what cytokines do Tr1 release?
IL-10
what cytokines do Th3 release?
TGF beta
what do effector CD4+ Th cells do?
help us fight pathogens
what do regulatory CD4+ Th cells do?
regulate/damoen the effectors
what makes up the organized tissues in GALT?
peyers patches
isolated lymphoid follicles
mesenteric lymph nodes
what makes up GALT?
the multi-follicular Peyer’s patches of the ileum
the vermiform appendix
the numerous isolated lymphoid follicles which are distributed along the length of the intestine
what are the specialized epithelial cells of peyers patches?
Microfold (M) cells
what are M cells function?
actively transport luminal antigens to the underlying lymphoid follicles to initiate an immune response - they pass the antigens to dendritic cells (transcyotosis)
whats the most abundant antibody in mucosal secretions?
iga
what is lamina propria?
connective tissue areas containing activated immune cells
whats the difference between IgA in the blood and in mucosal tissue?
in the blood IgA is monomeric and in the mucosal tissue its dimeric
whats the structure of dimeric IgA?
2 IgA connected by a J chain
how does secretory IgA form?
The dimeric IgA-J chain complex is produced by B lymphocytes in the submucosal tissues. The secretory component is produced by mucosal epithelial cells and acts as a receptor for dimeric IgA.
whats the function of secretory IgA?
limits the acess of pathogens to the mucosal surfaces without risking inflammatory damage
Why doesnt the commensal flora trigger inflammation?
TLR4 is expressed at the base of the crypts where you wouldnt see many commensals. TLR5 is expressed on the basolateral side. So pathogens invading tissues can trigger TLR activation unlike commensals.
Pathogens often have virulence factors unlike commensals.
Commensals can actually change their flagellin sequence so it doesnt bind as strongly to TLR5 making them TLR5 hyporesponsive.
