Gut Immune System Flashcards
what are the 3 factors that contribute to innate gut immunity?
commensal gut flora
epithelial barrier
biochemical factors produced by epithelial cells
how is commensal gut flora obtained?
At birth through birth canal: sterile gut –> obtains bacteria from the mother’s birth canal
how does breast milk contribute to the gut flora of babies?
insulin-like fructans = prebiotics that encourage the growth of microbes
what is the 3rd constituent of commensal gut flora?
probiotics
what are the positives of the commensal gut flora?
oral tolerance intestinal motility resistant to pathogen colonisation stimulate local immunity nutrition epithelial cell turnover
what are the negatives of commensal gut flora?
diseases of the GI tract e.g. IBS, H.pylori
extra-intestinal –> septicaemia
autoimmunity
allergy
how is the epithelial barrier renewed?
stem cells at the base of crypts of lieberkuhn –> self-renewing system
what do goblet cells secrete and what is their role?
mucins –> mucous layer
what is the role played by enterocytes in innate gut immunity?
cilia remove poorly adhered microbes
secrete antimicrobial peptides and proteins
what are the 2 aspects of specific gut immunity?
GALT and widespread leucocytes
which leucocytes are most numerous in the intraepithelial layer?
CD8 T cells, large granular
which leucocytes are most numerous in the lamina propria?
CD4 leucocytes
what are the 2 types of CD8 Tk cells?
A and B
Which cytokines do A type CD8 leucocytes secrete?
IL-2, IFN-y, CCL5
cytotoxic cells –> perforin granzyme
what is the role of type B CD8 leucocytes?
homeostasis
what are the 3 types of CD4 leucocytes?
Th-1, Th-2, Th-17
what is GALT?
gut associated lymphoid tissue
what 2 types of follicles exist along the length of the GI tract?
single isolated along the length of the GI tract aggregated follicles (Peyer's patches) - lymphoid structures associated with villi
Where are peyer’s patches most numerous?
ileum and appendix
What is the role of paneth cells?
secrete lysosomal enzymes and other substances into the crypt lumen
Which cells take up antigens through the epithelial barrier?
M cells
Which APCs are the antigens presented to?
dendritic cells
Which cells do the APCs present the antigen to?
T or B cells
What happens after the B cells travel to the mesenteric lymph nodes?
B cells differentiate –> plasma cells –> IgA
what is the purpose of the majority of inductive responses?
oral tolerance
What do dendritic cells do?
sample lumen –> naive T cells differentiate into regulatory T cells –> tolerance (active suppression/ clonal anergy)
How is IgA transported across the epithelium?
Active transport by endocytic vacuole
what is IgA secreted in?
colostrum, maternal milk, saliva, tears
What is the role of IgA?
neutralises viruses and toxins, enhances non-specific defence mechanisms (lactoferrin, lactoperidase), relatively resistant to proteolysis
what does IgA inhibity?
bacterial adhesion
macromolecule absorption
inflammatory effects of other Igs
