Gut Immune System

Question 1

what are the 3 factors that contribute to innate gut immunity?

Answer 1

commensal gut flora
epithelial barrier
biochemical factors produced by epithelial cells

Question 2

how is commensal gut flora obtained?

Answer 2

At birth through birth canal: sterile gut –> obtains bacteria from the mother’s birth canal

Question 3

how does breast milk contribute to the gut flora of babies?

Answer 3

insulin-like fructans = prebiotics that encourage the growth of microbes

Question 4

what is the 3rd constituent of commensal gut flora?

Answer 4

probiotics

Question 5

what are the positives of the commensal gut flora?

Answer 5

oral tolerance
intestinal motility
resistant to pathogen colonisation
stimulate local immunity
nutrition
epithelial cell turnover

Question 6

what are the negatives of commensal gut flora?

Answer 6

diseases of the GI tract e.g. IBS, H.pylori
extra-intestinal –> septicaemia
autoimmunity
allergy

Question 7

how is the epithelial barrier renewed?

Answer 7

stem cells at the base of crypts of lieberkuhn –> self-renewing system

Question 8

what do goblet cells secrete and what is their role?

Answer 8

mucins –> mucous layer

Question 9

what is the role played by enterocytes in innate gut immunity?

Answer 9

cilia remove poorly adhered microbes

secrete antimicrobial peptides and proteins

Question 10

what are the 2 aspects of specific gut immunity?

Answer 10

GALT and widespread leucocytes

Question 11

which leucocytes are most numerous in the intraepithelial layer?

Answer 11

CD8 T cells, large granular

Question 12

which leucocytes are most numerous in the lamina propria?

Answer 12

CD4 leucocytes

Question 13

what are the 2 types of CD8 Tk cells?

Answer 13

A and B

Question 14

Which cytokines do A type CD8 leucocytes secrete?

Answer 14

IL-2, IFN-y, CCL5

cytotoxic cells –> perforin granzyme

Question 15

what is the role of type B CD8 leucocytes?

Answer 15

homeostasis

Question 16

what are the 3 types of CD4 leucocytes?

Answer 16

Th-1, Th-2, Th-17

Question 17

what is GALT?

Answer 17

gut associated lymphoid tissue

Question 18

what 2 types of follicles exist along the length of the GI tract?

Answer 18

single isolated along the length of the GI tract
aggregated follicles (Peyer's patches) - lymphoid structures associated with villi

Question 19

Where are peyer’s patches most numerous?

Answer 19

ileum and appendix

Question 20

What is the role of paneth cells?

Answer 20

secrete lysosomal enzymes and other substances into the crypt lumen

Question 21

Which cells take up antigens through the epithelial barrier?

Answer 21

M cells

Question 22

Which APCs are the antigens presented to?

Answer 22

dendritic cells

Question 23

Which cells do the APCs present the antigen to?

Answer 23

T or B cells

Question 24

What happens after the B cells travel to the mesenteric lymph nodes?

Answer 24

B cells differentiate –> plasma cells –> IgA

Question 25

what is the purpose of the majority of inductive responses?

Answer 25

oral tolerance

Question 26

What do dendritic cells do?

Answer 26

sample lumen –> naive T cells differentiate into regulatory T cells –> tolerance (active suppression/ clonal anergy)

Question 27

How is IgA transported across the epithelium?

Answer 27

Active transport by endocytic vacuole

Question 28

what is IgA secreted in?

Answer 28

colostrum, maternal milk, saliva, tears

Question 29

What is the role of IgA?

Answer 29

neutralises viruses and toxins, enhances non-specific defence mechanisms (lactoferrin, lactoperidase), relatively resistant to proteolysis

Question 30

what does IgA inhibity?

Answer 30

bacterial adhesion
macromolecule absorption
inflammatory effects of other Igs