GI immunology Flashcards

1
Q

what is Payer’s patch

A

a specialised area where gut contents are sampled

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2
Q

what is Payer’s patch covered in

A

epithelial layer containing M cells

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3
Q

what are M cells

A

specialised cells which have characteristic membrane ruffles

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4
Q

what is the function of M cells

A

gateway for antigens into payer’s patch:

take up antigen via endocytosis and phagocytosis

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5
Q

where are dendritic cells located within the payer’s patch

A

directly under M cells

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6
Q

how do dendritic cells bring antigens into the payers patch

A

extend processes across the epithelial layer to capture antigens from the lumen of the gut

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7
Q

how are antigens brought into the Payer’s patch (2)

A
  1. M cells = endocytosis & phagocytosis

2. dendritic cells = extend processes

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8
Q

what are the 2 distinct compartments of the mucosal immune system

A

the epithelium

the lamina propria

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9
Q

what immune cells are located within the lamina propria

A

ALL types

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10
Q

what immune cells are located within the epithelia

A

dendritic cells

T cells

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11
Q

what is the percentage breakdown of the intestinal response

A
80% = IgA
IgM = 15%
IgG = 5%
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12
Q

describe the IgA in the intestinal response

A

dimeric

IgA1:IgA2 = 3:2

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13
Q

describe T cells role within the GI system

A

T cells enter Payers patch from blood vessels directed by L-selectin

They encounter antigens and are transported across M cell where they are activated by dendritic cells

activated T cells drain via mesenteric lymph nodes to the thoracic duct and return to the blood.

gut homing effector T cells bind to MAdCAM1 on endothelium

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14
Q

what is the role of MAdCAM

A

binds gut homing effector T cells on the endothelium

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15
Q

what does IgA bind to

A

poly-Ig receptor

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16
Q

what can IgA be replaced by and why

A

IgM

they are both polymers

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17
Q

what are intraepithelial lymphocytes (IELs)

A

CD8+ T cells

18
Q

where are intraepithelial lymphocytes (IELs) located

A

lie within the epithelia lining of the gut

19
Q

how do are intraepithelial lymphocytes (IELs) react to viruses

A

infected cells displayed viral peptide to IEL via MHC class 1

activated IEL kill the infected epithelia cell

20
Q

what do stressed epithelial cells express

A

MIC-A and MIC-B

21
Q

how do IEL bind to MIC-A and MIC-B, what happens next

A

via NKG2D

this then activated the IEL which then kills the stressed cell

22
Q

give examples of mucosal disorders associated with primary immunodeficiency

A
selective IgA deficiency 
CVID = Common variable immune deficiency
XLA = X-linked agammaglobulinemia
CGD = Chronic Granulomatous Disease
SCID
23
Q

what condition is IgA associated with

A

coeliac disease

24
Q

what are the symptoms of Common variable immune deficiency (CVID)

A

recurrent sinopulmonary and GI infections

25
Q

what is the cause of Common variable immune deficiency (CVID)

A

failure to differentiate into Ig secreting cells

low IgG, IgA, IgM, and IgE

26
Q

what are the symptoms of X-linked agammaglobulinemia (XLA)

A

sinopulmonary and GI infections + chronic enteroviral infections

27
Q

what is the cause of X-linked agammaglobulinemia (XLA)

A

no B cells/ agammaglobulinemia

28
Q

what is the cause of SCID

A

defect in T and B cell immunity

29
Q

what are the symptoms of SCID

A

oral candidiasis

chronic diarrhoea interstitial pneumonitis

30
Q

what is the cause of Chronic Granulomatous Disease (CGD)

A

failure of phagocyte respiratory burst

31
Q

what are the symptoms of Chronic Granulomatous Disease (CGD)

A

staph aureus infections

perianal, liver, and skin abscess

32
Q

what type of hypersensitivity is a food allergy

A

type 1

33
Q

how are food allergies initiated

A

cross linking of allergen specific IgE on the surface of mast cells with the specific allergen

34
Q

what Ig is involved in food allergies

A

IgE

35
Q

describe the villi in coeliac disease

A

flattened with “scalloping”

villous atrophy

36
Q

what genes are associated with coeliac disease

A

HLADQ2

HLADQ8

37
Q

describe the immunological process involved in coeliac disease

A

Gamma interferon from gluten specific T cells activate epithelia cells which produce IL-15 which induces proliferation and activation IEL. both T cells and IEL then kill the epithelia cells

38
Q

what IL is involved in coeliac disease

A

IL-15

39
Q

how is coeliac disease diagnosed

A

biopsy (gold standard in kids)

serology for IgA anti-TTG

40
Q

what is crohn’s disease mediated by

A

Th1 CD4+ T cells
gamma interferon
IL-12
TNF alpha

41
Q

what gene is associated with crohn’s disease

A

NOD2

42
Q

what IL are associated with crohn’s disease

A

IL-12 (main one)
IL-8
IL-23