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LC Gastroenterology Week 2 > Mucosal Immunity Basic Science > Flashcards

Mucosal Immunity Basic Science Flashcards

1
Q

Name 4 physiological functions of mucosal tissues?

A

Gas exchange
Food absorption
Sensory activities
Reproduction

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2
Q

What does the mucosal tissues require?

A

Effective defence mechanisms as they are highly vulnerable due to fragility and permeability. It is a portal of entry for non pathogenic antigens

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3
Q

What is a mucous membrane?

A

A mucous membrane or mucosa is a membrane that lines various cavities in the body and surrounds internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue.

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4
Q

What are some distinctive features of the GUT mucosal immune system?

  • anatomical
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

What are some distinctive features of the GUT mucosal immune system?

  • effector mechanisms
A

Activated/memory T cell predominate

“natural” effector /regulatory T cells

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6
Q

What are some distinctive features of the GUT mucosal immune system?

  • Immunoregulatory environment
A

Active down regulation of immune response

Inhibitory macrophages and tolerising dendritic cells

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7
Q

What is the Gi tract?

A

A lymphoid organ

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8
Q

What are lymphocytes?

A

A lymphocyte is one of the subtypes of white blood cell in a vertebrate’s immune system. Lymphocytes include natural killer cells (NK cells) (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). They are the main type of cell found in lymph, which prompted the name “lymphocyte”.

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9
Q

What are the 3 different types of lymphoid populations you find in the GUT?

A

Peyer’s Patches (Organised lymphoid tissues)

Lamina propria lymphocytes (scattered lymphoid cells)

Intraepithelial lymphocytes (scattered lymphoid cells)

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10
Q

Describe Peyer’s patches?

A

Located in the mucosa, go down to submucosa
Covered in epithelial layers containing specialised cells called M cells which have characteristic membrane ruffles.

Inside there are germinal centres within a follicle

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11
Q

What are M cells, describe how they sample antigens?

A

The are microfilm cells

They take up an antigen in the lumen by endocytosis and phagocytosis
The antigen is transported across the M cells in vesicles and released at the basal surface into the Payer’s Patch
Antigen is bound by dendritic cells which then activate T cells

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12
Q

Describe how dendritic cells can also sample antigens in the lumen?

A

The can push pseudopods between the epithelial layer to capture the antigen from the lumen of the gut

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13
Q

Describe how T cells enter the Payer’s patch?

A

From the blood vessels, directed by the homing receptors CCR7 and L-selectin

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14
Q

Describe what the T cells do once in the Payer’s Patch?

A

The encounter an antigen transported across the M cell and become activated by dendritic cells

The activated T cells drain via mesenteric lymph nodes to the thoracic duct and return to the gut via the bloodstream

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15
Q

Can Lymphocytes primed in the gut can migrate to other mucosal sites?

A

Yes

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16
Q

what is the primary immunoglobulin found in the gut?

A

IgA

17
Q

What happens with the IgA how does it get from epithelial cells to the lumen?

A

It is transported across the epithelial cells in a vesicle and then released once it gets to the apical face of the epithelial cell

18
Q

What can IgA do in the gut?

A

It can bind and neutralise pathogens and toxins in the lumen
It can also bind and neutralise antigens internalised in endoscopes
It can also export toxins and pathogens from the lamina propria whiles its being secreted

19
Q

Describe the specialised T cells in the gut? (??)

A

Intraepithelial lymphocytes

  • CD8 - positive T cells
  • 2 types with different recognition mechanisms
  • Activated appearance containing full killing machinery
20
Q

Describe what happens when a virus infects a mucosal epithelium cell?

A 
The infected cell displays viral peptide to CD8 intraepithelial cell via MHC class 1 
The activated intraepithelial cell kills the infected epithelia cell by perforin/granzyme and Fas-dependent pathways
21
Q

What type of organisms help regulate local hypo responsiveness?

A

Commensal organisms - PPAR gamma

22
Q

What is the role of intestinal mucosal immunity in disease?

A 
Infectious disease
Primary immunodeficiency
Allergy
Coeliac disease
IBD
23
Q

What type of mechanisms eliminate most intestinal infections rapidly?

A

Innate mechanisms

24
Q

How is the mucosal response to infection activated?

A

Activation through ligation of pattern recognition receptors

25
Q

What do the intracellular sensors in the epithelial cells do in response to infection/

A

Pattern recognition receptors activate the NFkB pathway

There is then gene transcription and productive of cytokines, chemokine’s and defending which activates the underlying immune response

26
Q

What is the outcome of infection by intestinal pathogens determined by?

A

A complex interplay between the microorganism and the host.

27
Q

Name a Mucosal disorder associated with primary immunodeficiency?

A

Selective IgA deficiency - (coeliac disease)

SCID - profound defect in T and B cell immunity

28
Q

Describe what happens in a food allergy?

A

Type I 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

29
Q

Describe Coeliac disease?

A

(autoimmune, causes damage to small intestine leading to malnutrition)

Not an allergy
Antigenic target gluten
Immunopathology Tell/IEL mediated

Gamma interferon from Gluten specific T cell activate epithelial cells which produce IL-15 which induces proliferation and activation of IEL
Both T cells and IEL can then kill epithelial cells (villous atrophy)

30
Q

What is the gold standard for diagnosing coeliac?

A

Biopsy

Serology good for screening Isa anti tissue trasnglutaminase autoantibodies - if there is no gluten there will be non of this present

31
Q

What is IgA anti-TTG mainly used for?

A

IgA anti-TTG is used for dietary compliance monitoring

32
Q

What is Crohns disease mediated by?

A

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

33
Q

What is Ulcerative colitis restricted to?

A

The rectum and colon - inflammation just in the surface of mucosal

LC Gastroenterology Week 2 (6 decks)

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