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
what is the cause of Common variable immune deficiency (CVID)
failure to differentiate into Ig secreting cells low IgG, IgA, IgM, and IgE
26
what are the symptoms of X-linked agammaglobulinemia (XLA)
sinopulmonary and GI infections + chronic enteroviral infections
27
what is the cause of X-linked agammaglobulinemia (XLA)
no B cells/ agammaglobulinemia
28
what is the cause of SCID
defect in T and B cell immunity
29
what are the symptoms of SCID
oral candidiasis | chronic diarrhoea interstitial pneumonitis
30
what is the cause of Chronic Granulomatous Disease (CGD)
failure of phagocyte respiratory burst
31
what are the symptoms of Chronic Granulomatous Disease (CGD)
staph aureus infections | perianal, liver, and skin abscess
32
what type of hypersensitivity is a food allergy
type 1
33
how are food allergies initiated
cross linking of allergen specific IgE on the surface of mast cells with the specific allergen
34
what Ig is involved in food allergies
IgE
35
describe the villi in coeliac disease
flattened with "scalloping" | villous atrophy
36
what genes are associated with coeliac disease
HLADQ2 | HLADQ8
37
describe the immunological process involved in coeliac disease
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
what IL is involved in coeliac disease
IL-15
39
how is coeliac disease diagnosed
biopsy (gold standard in kids) | serology for IgA anti-TTG
40
what is crohn's disease mediated by
Th1 CD4+ T cells gamma interferon IL-12 TNF alpha
41
what gene is associated with crohn's disease
NOD2
42
what IL are associated with crohn's disease
IL-12 (main one) IL-8 IL-23