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GI > Immunology > Flashcards

Immunology Flashcards

1
Q

Describe the physiological function of mucosal tissues

A
  • gas exchange
  • food absorption
  • sensory activities
  • reproduction
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2
Q

Name the mucosal tissues of the human body

A
  • lachrymal gland
  • salivary gland
  • gastro-intestinal gland
  • kidney
  • mammary gland
  • uterus
  • bladder
  • vagina
  • oral cavity
  • sinus
  • conjunctive
  • oesophagus
  • stomach
  • intestine
  • trachea
  • lungs
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3
Q

Name the sections of a lymph node

A
  • cortical sinus
  • secondary lymphoid follicle (with germinal centre)
  • afferent lymphatic vessel
  • paracortical area (mostly T cells)
  • germinal centre
  • marginal sinus
  • senescent germinal centre
  • efferent lymphatic vessel
  • artery
  • vein
  • medullary sinus
  • medullary cords (macrophages and plasma cells)
  • primary lymphoid follicle (mostly B cells)
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4
Q

Describe the distinctive anatomical features of gut mucosal immune system

A
  • intimate relationship between mucosal epithelia and lymphoid tissue
  • organised lymphoid structures unique to mucosal sites
  • specialised antigen uptake mechanisms
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5
Q

Describe the distinctive effector mechanism of gut mucosal immune system

A
  • activated / memory T cells predominate

- natural effector / regulatory T cells

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6
Q

Describe the distinctive immunoregulatory environment of gut mucosal immune system

A
  • active down regulation of immune response

- inhibitory macrophages and tolerising dendritic cells

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7
Q

Where are intestinal lymphocytes found?

A

In organised tissues where immune responses are induced and scattered throughout the intestine, where they carry out effector functions

  • scattered lymphoid tissues
  • organised lymphoid tissues
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8
Q

Describe peyers patches

A
  • covered by an epithelial layer containing specialised cells called M cells
  • M cells have characteristic membrane ruffles
  • antigen catchers and reaction vesicle
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9
Q

How do M cells take up antigens?

A
  • endocytosis

- phagocytosis

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10
Q

How can dendritic cells capture antigens from the lumen of the gut?

A

They can extend processes across the epithelial layer

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11
Q

The mucosal immune system consists of which two distinct compartments?

A
  • epithelium

- lamina propria

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12
Q

T cells enter peyers patches from blood vessels, directed by what?

A

Homing receptors

  • CCR7 and L-selectin
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13
Q

What binds MAdCAM-1 on endothelium?

A

Gut homing effector T cells

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14
Q

Gut epithelial cells express what specific for gut homing T cells?

A

Chemokines

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15
Q

Where is MAdCAM also found?

A

In the vasculature of other mucosal sites

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16
Q

Secreted IgA on the gut surface can do what to pathogens and toxins?

A

Can bind and neutralise

17
Q

What can export toxins and pathogens from the lamina propria while being secreted?

A

IgA

18
Q

What is able to bind and neutralise antigens internalised in endosomes?

A

IgA

19
Q

Describe intraepithelial lymphocytes

A
  • special T cells in the gut
  • activated appearance containing full killing machinery
  • restricted antigen receptor repertoire
  • expression of alpha e ; beta 7 integrin anchors them in the epithelium
  • 2 types with different recognition mechanisms
  • immunopathology coeliac disease
20
Q

Where do intraepithelial lymphocytes lie?

A

Within the epithelial lining of the gut

21
Q

The intraepithelial lymphocytes are what type of cell?

A

CD8- positive T cells

22
Q

Activated IEL kills infected epithelial cells by what?

A

Perforin / granzyme and Fas-dependent pathways

23
Q

Epithelial cells undergo stress as a result of what?

A

Infection, damage or toxic peptides and express MIC-A and MIC-B

24
Q

What binds to MIC-A,B to activate IEL?

A

NKG2D

25
Q

Describe some of the proposed mechanisms of mucosal hypo responsiveness

A
  • commensal organism help regulate local hypo-responsiveness PPAR gamma
  • anergy or deletion of antigen specific T cells, no costimulation
  • generation of regulatory T cells particularly CD4+ TGF beta producing TH3 cells, weak costimulation
26
Q

What initiates a cascade of signal that activates IKK?

A

Pathogen recognition by TLRs

27
Q

IKK phosphorylates what?

A

IKB - targeting it to be degraded

28
Q

What happens during the presence of commensal bacteria?

A

Production of PGE2, TGF-beta and TSLP inhibits dendritic cell maturation

29
Q

Describe the mucosal response to infection and regulation of mucosal immune responses

A
  • innate mechanisms eliminate most intestinal infections rapidly
  • activation through ligation of pattern recognition receptors
  • intracellular sensors in epithelial cells, PRR, activate the NfkB pathway
  • gene transcription and production of cytokines, chemokines and defensins
  • activation of underlying immune response
30
Q

The outcome of infection by intestinal pathogens is determined by what?

A

A complex interplay between the microorganism and the host IR

31
Q

Describe selective IgA deficiency

A
  • 2/3 asymptomatic remainder recurrent sinopulmonary infections
32
Q

Describe CVID

A
  • recurrent sinopulmonary and GI infections
  • failure to differentiate into Ig secreting cells
  • low IgG, IgA, IgM, and IgE
  • defective antigen specific antibody response
33
Q

Describe XLA

A
  • sinopulmonary and GI infection and devastating systemic manifestations of chronic enteroviral infections
  • no B cell / agammaglobulinaemia
34
Q

Describe CGD

A
  • staphylococcus aureus / inflammatory granulomas-pneumona, liver abscess, perianal abscess and skin abscess
  • failure of phagocyte respiratory burst
35
Q

Describe SCID

A
  • profound defect in T and B cell immunity
  • oral candidiasis
  • chronic diarrhoea
  • interstitial pneumonitis
  • GI-CMV, rotavirus, EBV
36
Q

Describe food allergies

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
37
Q

Describe coeliac disease / gluten sensitive enteropathy

A
  • genetically linked autoimmune disorder, causes damages to the small intestine leading to malnutrition
  • life long, incurable
  • it is not an allergy
  • antigenic target gluten
  • trigger unknown
  • genetic susceptibility
  • immunopathology T cell/ IEL mediated
  • gamma interferon from gluten specific T cell activates epithelial cells which produce IL-15 which induces proliferation and activation of IEL
  • both T cells and IEL can then kill epithelial cells
38
Q

Describe crohns disease

A
  • can affect any part of the GI tract from the mouth to the anus, commonly distal ileum and colon
  • focal and discontinuous inflammation with deep and eroding fissures +/- granulomas
  • mediated by TH1 CD4+Tcells / gamma interferon / IL-12/ TNF alpha
  • multiple genetic deficiency and immunologic mechanisms - HLA
  • gene identified NOD2
  • intracellular PRR-muramyl dipeptide of bacterial peptidoglycan
  • IL-8 (CXCL8) and neutrophil function
  • IL-23/ autophagy
39
Q

Describe ulcerative colitis

A
  • restricted to rectum and colon
  • starts in rectum and moves proximally and contiguously, can develop extra-intestinal manifestations
  • distortion of the crypts with infiltration of monocytes / neutrophils and plasma cells
  • inflammation and ulceration just in surface mucosa
  • immunopathology unclear does not fit into TH1/TH2 split
  • postulated may be an NK T cell mediated disease via IL-13

GI (11 decks)

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