Immunology

Question 1

what do goblet cells produce?

Answer 1

mucus

Question 2

what do paneth cells produce?

Answer 2

defensins

Question 3

what is the function of peyers patches?

Answer 3

antigen sampling and immune activation

Question 4

compare small intestine and large intestine in terms of crypts and villi?

Answer 4

small intestine has both villi and crypts

large intestine has only crypts- no villi

Question 5

compare goblet cells in the small intestine and large intestine?

Answer 5

more goblet cells in large intestine than small intestine

Question 6

where are paneth cells found?

Answer 6

small intestine 
(none in large intestine)

Question 7

where are peyers patches found?

Answer 7

lamina propria of small intestine

none in large intestine

Question 8

what type of cells do peyers patches contain?

Answer 8

macrophages
dendritic cells
intra-epithelial lymphocytes
effector T cells
IgA secreting plasma cels
innate lymphoid cells
stromal cells (eg fibroblasts)

Question 9

apart from in peyers patches, how else can antigen presentation in the gut occur?

Answer 9

directly across epithelium

Question 10

what immune cells extend across the epithelial layer to capture antigens?

Answer 10

dendritic cells

Question 11

what are peyers patches covered with?

Answer 11

an epithelial layer containing M cells

Question 12

what is the function of M cells?

Answer 12

M cells sieve antigens through into peyers patches

Question 13

how do M cells take up antigen?

Answer 13

via endocytocis and phagocytosis

Question 14

what happens if a dendritic cell within a peyers patch or directly across the epithelium takes up an antigen while in the right pro-inflammaroty state?

Answer 14

the dendritic cell will migrate to the mesenteric lymph nodes to present the antigen and stimulate acquired immune response

Question 15

what is the most common antigen type in the gut?

Answer 15

IgA

Question 16

how are circulating T cells directed to Peyers patches from the blood vessels?

Answer 16

CCR7 and L-selectin are homing receptors which direct the T cells

Question 17

once a T cell has become activated by dendritic cells from peyers patches what integrin and chemokine become expressed?

Answer 17

a4b7 and CCR9

Question 18

what do a4b7 and CCR9 allow the T cell to do?

Answer 18

home to the lamina propria and intestinal epithelium of the small intestine

Question 19

what is the function of chemokine CCR7?

Answer 19

allows T cells to keep recirculating

Question 20

what happens to CCR7 when a T cell has become activated?

Answer 20

CCR7 is no longer expressed

Question 21

what adhesion molecule on the endothelium does the a4b7 on the activated T cell bind to?

Answer 21

MAdCAM-1

Question 22

what chemokine is specific to the small intestine and attracts the CCR9 on the activated T cell?

Answer 22

CCL25

Question 23

when might IgG be the most abundant antibody in the gut?

Answer 23

flare of ulcerative colitis

Question 24

compare immunoglobulin structure in the circulation to structure in the gut?

Answer 24

dimeric in the gut

monomeric in circulation

Question 25

in a dimeric immunoglobulin what joins the 2 immunoglobulins together?

Answer 25

J chain | joining chain

Question 26

why does IgA coat the lumen of the cut?

Answer 26

creates an immune barrier

Question 27

why must immunoglobulins keep being produced for the immune barrier to maintain?

Answer 27

because IgA is constantly lost from the barrier during gut contractions and absorption of food

Question 28

what is the function of the poly-Ig receptor?

Answer 28

binds to the IgA dimer and facilitates endocytosis across the basal membrane

Question 29

what happens when the IgA dimer-poly-Ig-receptor complex gets to the lumenal membrane?

Answer 29

the poly-Ig receptor is cleaved but a remnant (secretory piece) still remains on the IgA which goes into the lumen

Question 30

what is the function of the secretory piece that is bound to the IgA in the lumen of the GI tract?

Answer 30

prevents IgA being digested | remember immunoglobuls are proteins

Question 31

what are intraepithelial lymphocytes?

Answer 31

pre-activated lymphocytes (mainly cytotoxic)

Question 32

what is the importance of mucosal hyporesponsiveness?

Answer 32

so the immune system isn't attacking every antigen (most non-pathogenic) found in the gut lumen

Question 33

what is anergy of specific T cells?

Answer 33

switching off of specific T cells (ie specific to non pathogenic antigen) so they will not attack cell

Question 34

what 2 factors cause anergy of T cells?

Answer 34

high TGFbeta (transforming growth factor beta) and low pro-inflammatory cytokines

Question 35

what microscopic changes causes scalloping of the small intestine seen in coeliacs disease?

Answer 35

villous atrophy | total loss of villi

Question 36

what is the gold standard for diagnosis of coeliacs?

Answer 36

biopsy

Question 37

what serology test is a very useful screening test fo coeliacs disease?

Answer 37

serology for IgA anti-TTG | anti-tissue transglutaminase auto antibodies

Question 38

when might you get a false negative on serology testing for coeliacs disease?

Answer 38

IgA deficiency | patient hasn't eaten gluten

Question 39

what is the main cause of persistent symptoms of Coeliacs disease?

Answer 39

lack of compliance

Question 40

compare the parts of the GI tract that ulcerative colitis and crohns affect?

Answer 40

UC- colon (rectum+proximally) | Crohns- any part with skip lesions

Question 41

compare the depth of inflammation of the GI tract that ulcerative colitis and crohns affect?

Answer 41

UC- mucosal | Crohns- transmural/granulomatous

Question 42

which has a greater genetic link- crohns or UC?

Answer 42

crohns

Question 43

compare the types of CD4 T cells involed in crohns and UC?

Answer 43

UC- Th2 | Crohns- Th1

Question 44

what type of hypersensitivity reaction is a food allergy?

Answer 44

type 1 hypersensitivity

Question 45

what is the usual hypersensitivity response to food?

Answer 45

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