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Gastrointestinal System > Mucosal Immunity > Flashcards

Mucosal Immunity Flashcards

1
Q

mucosal tissue

A

gas exchange
food absorption
sensory activities
reproduction

all functions critical to life

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2
Q

epithelial cells

A 
passive but selective
variable and regulated
transcellular
tight junction
paracellular
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3
Q

afferent lymphatic vessel

A

brings antigens into lymph node

mostly on dendrites

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4
Q

gut mucosal immune system

A

specialised antigen organisation and uptake

memory T cell predominate

immunoregulatory environment

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5
Q

peyers patch

A

covered by an epithelial layer containing specialised cells called M(mricofoam) cells which have characteristic membrane ruffles

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6
Q

m cells are often a target for pathogen

A

due to less mucosal protection

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7
Q

how do m cells take up antigens

A

endocytosis and phagocytosis

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8
Q

antigen is transported across the m cells in vesicles

A

released at the basal surface

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9
Q

actives T cells

A

due to antigen binding by dendritic cells

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10
Q

dendritic cells

A

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

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11
Q

what does the mucosal immune system consist of

A

distinct compartments

epithelium and lamina propria

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12
Q

lamina propria

A

dendritic cell, plasma cell macrophage, CD4 & 8 T cell, mast cell, IgA

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13
Q

epithelial layer

A

CCR9, DC,

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14
Q

alpha4-beta7 integrin

A

coeliac disease

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15
Q

T cells enter peyers patches

A

directed by the homing receptors CCR7 and l-selectin

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16
Q

T cells in peyers

A

encounter antigen transported across m cells and become activated by dendritic cells

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17
Q

activated t cells

A

drain bua mesenteric lymph nodes to the thoracic duct and return to the gut via bloodstream

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18
Q

activated T cells expressing alpha4-beta7 integrin and CR9

A

home to the lamina propria and intestinal epithelium of small intestine

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19
Q

MadCAM-1 on endothelium

A

gut-homing effector T cells bind

found in the vasculature at musical sites

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20
Q

humoral intestinal response

A

IgA - mostly produced in gut

IgA1 : IgA2

3: 2 = gut
10: 1 = periphery

dimeric - four antigen binding sites

IgM
IgG

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21
Q

systemic hormal immune repsonse

A

reversal

IgA - monomeric

22
Q

IgA is transported across the lumen of the gut

A

binds to receptor on basolateral face of epithelial cell

endocytosis

transcytosis to apical face of epithelial cell

release of IgA dimer at apical face of epithelial cell

23
Q

secreted IgA

A

binds and neutralises pathogens and toxins on the gut surface

bind and neutralise antigens internalised in endosomes

export toxins and pathogens from the lamina propria while being secreted

24
Q

special T cells in the gut

A

intraepithelial lymphocytes

expression of aphaE:beta7 intern anchors them in the epithelium

2 types with different recognition mechanism

25
Q

intra-epithelial lymphocytes (IELs)

A

lie within the epithelial lining of the gut

CD8+ T cells

26
Q

virus infects mucosal epithelium cell

A

infected cell displays viral peptide to CD8 IEL via MHC class 1

activated IEL kills infected epithelial cell by perforin/granzyme and fas-dependent pathways

27
Q

epithelial cells undergo stress as a result of infection

A

express MIC-A and MIC-B

NKG2D on IELs bind to MIC-A,B and activated IEL

CD8 alpha:alpha homodimers also bind to TL

28
Q

activated IEL

A

kills the stressed cell via the perforin/granzyme pathway

29
Q

balance between protective immunity and homeostasis

A

discriminating between pathogen and innocuous antigens

oral tolerance

T and IgE responses inhibited more than IgG responses

30
Q

mucosal hyporesponsiveness

A

commensal organisms help regulate local hyporesponsiveness - PPAR gamma

anergy or deletion of antigen specific T cells - no costimulation

generation of regulatory T cells - weak costimulation

31
Q

role of intestinal mucous immunity in disease

A 
infectious disease
primary immunodeficiency 
allergy
coeliac disease
IBD
32
Q

mucosal response to infection and regulation of mucosal immune reponses

A

innate mechanisms eliminate most intestinal infections rapidly

activation through ligation of pattern recognition receptors

intracellular sensore in epithelial cells, PRR, activate the NFkB pathway

gene transcription and production of cytokines, chemokine and defensives

activation of underlying immune response

33
Q

outcome of infection by intestinal pathogens

A

determined by a complex interplay between the microorganisms and the host IR

34
Q

naive CD4 T cells are activated

A

during helminth infection and can differentiate to Th1 or Th2 effector cells

35
Q

Th2 cell effector functions

A

produce IL-13, IL-5
induces epithelial cell repair and mucus and activated eosinophils

drive B cells to produce IgE

drive mast cell recruitment via IL-3, IL-9
specific IgE arms mast cels against helminths

36
Q

Th1 cell effector functions

A

activate macrophages

activate B cells to produce IgG2a

37
Q

infected dendritic cells

A

shuttle virus from the site of exposure to the regional lymph nodes where they concentrate virus particles and infect CD4+ T cells

38
Q

mucosal disorder associated with primary immunodeficienct

A

all associated with mucosal abnormalities

39
Q

CVID - adults

A

recurrent sinopulmonary and GI infections

failure to differentiate into Ig secreting cells

40
Q

XLA - childhood. after 6 months of age

A

sinoplumonary and GI infections and devastating systemic manifestations

no B cells / agammaglobulinaemia

41
Q

CGD - childhood

A

staphylococcus aureus/inflammatory granulomaspneumona, liver abscess, perianal abscess, skin abscess

failure of phagocyte respiratory burst

42
Q

SCID - childhood

A

profound defect in t and B cell immunity

43
Q

SCID - childhood

A

profound defect in t and B cell immunity

44
Q

food allergy

A

type 1 hypersensitivity reaction initiated by crosslinking of allergen specific IgE on the surface of mast cells with the specific allergen

memory response- immune system must be primed

45
Q

IgE secreted by plasma cells

A

binds to a high-affinity Fc receptor FcRI on mast cells

46
Q

activated mast cells

A

provide contact and secreted signals to B cells to stimulate IgE production

47
Q

coeliac disease - gluten sensitive enteropathy

A

genetically linked, autoimmune disorder

causes damage to the small intestine leading to malnutrition

tigger unknown

genetic susceptibility HLADQ2/HLADQ8
immunopathology T cell/IEL mediated

48
Q

coeliac disease has small intestine with villous atrophy

A

villi gone
epithelium damage

low absorption capacity - malnutrition

49
Q

diagnosing coeliac disease

A

NICE guidelines

biopsy - adults

serology - paediatrics
who goes for a biopsy
IgA anti-tissue transglutaminase autoantibodies

beware IgA deficiency and false negatives

50
Q

crohns disease

A

focal and discontinuous inflammation with deep and eroding fissures +/- granulomas

51
Q

ulcerative colitis

A

restricted to rectum and colon

starts in rectum and moves proximally and contiguously - can develop extra-intestinal manifestations

inflammation and ulceration just in surface mucosa

52
Q

ulcerative colitis - treatment

A

non specific anti-inflammatory and immunosuppressive drugs

Gastrointestinal System (43 decks)

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