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Gastrointestinal > Immunology > Flashcards

Immunology Flashcards

1
Q

what do goblet cells produce?

A

mucus

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2
Q

what do paneth cells produce?

A

defensins

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3
Q

what is the function of peyers patches?

A

antigen sampling and immune activation

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4
Q

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

A

small intestine has both villi and crypts

large intestine has only crypts- no villi

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5
Q

compare goblet cells in the small intestine and large intestine?

A

more goblet cells in large intestine than small intestine

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6
Q

where are paneth cells found?

A 
small intestine 
(none in large intestine)
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7
Q

where are peyers patches found?

A

lamina propria of small intestine

none in large intestine

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8
Q

what type of cells do peyers patches contain?

A 
macrophages
dendritic cells
intra-epithelial lymphocytes
effector T cells
IgA secreting plasma cels
innate lymphoid cells
stromal cells (eg fibroblasts)
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9
Q

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

A

directly across epithelium

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10
Q

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

A

dendritic cells

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11
Q

what are peyers patches covered with?

A

an epithelial layer containing M cells

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12
Q

what is the function of M cells?

A

M cells sieve antigens through into peyers patches

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13
Q

how do M cells take up antigen?

A

via endocytocis and phagocytosis

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14
Q

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?

A

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

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15
Q

what is the most common antigen type in the gut?

A

IgA

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16
Q

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

A

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

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17
Q

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

A

a4b7 and CCR9

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18
Q

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

A

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

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19
Q

what is the function of chemokine CCR7?

A

allows T cells to keep recirculating

20
Q

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

A

CCR7 is no longer expressed

21
Q

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

A

MAdCAM-1

22
Q

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

A

CCL25

23
Q

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

A

flare of ulcerative colitis

24
Q

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

A

dimeric in the gut

monomeric in circulation

25
Q

in a dimeric immunoglobulin what joins the 2 immunoglobulins together?

A

J chain

joining chain

26
Q

why does IgA coat the lumen of the cut?

A

creates an immune barrier

27
Q

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

A

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

28
Q

what is the function of the poly-Ig receptor?

A

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

29
Q

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

A

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

30
Q

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

A

prevents IgA being digested

remember immunoglobuls are proteins

31
Q

what are intraepithelial lymphocytes?

A

pre-activated lymphocytes (mainly cytotoxic)

32
Q

what is the importance of mucosal hyporesponsiveness?

A

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

33
Q

what is anergy of specific T cells?

A

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

34
Q

what 2 factors cause anergy of T cells?

A

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

35
Q

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

A

villous atrophy

total loss of villi

36
Q

what is the gold standard for diagnosis of coeliacs?

A

biopsy

37
Q

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

A

serology for IgA anti-TTG

anti-tissue transglutaminase auto antibodies

38
Q

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

A

IgA deficiency

patient hasn’t eaten gluten

39
Q

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

A

lack of compliance

40
Q

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

A

UC- colon (rectum+proximally)

Crohns- any part with skip lesions

41
Q

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

A

UC- mucosal

Crohns- transmural/granulomatous

42
Q

which has a greater genetic link- crohns or UC?

A

crohns

43
Q

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

A

UC- Th2

Crohns- Th1

44
Q

what type of hypersensitivity reaction is a food allergy?

A

type 1 hypersensitivity

45
Q

what is the usual hypersensitivity response to food?

A 
vomiting
diarrhoea
pruitis
urticaria
anaphylaxis (rarely)

Gastrointestinal (15 decks)

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