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Module 204 MSK & Immune system > T1 L11 Mucosal immunity > Flashcards

T1 L11 Mucosal immunity Flashcards

1
Q

What is mucosa-associated lymphatic tissue divided into?

A

Bronchial associated lymphatic tissue (BALT)

Gut associated lymphatic tissue (GALT)

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2
Q

Why is the mucosal immune system important?

A

Largest immune compartment of organism
In direct contact with outside environment
Mucosal sites are port of entry for many infections and target site for vaccine-induced protection

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3
Q

What is the estimated surface area of the mucosal immune system?

A

400m2

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4
Q

What are the HIV transmission routes?

A

Genitourinary
Rectal
Oral

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5
Q

What are the main mucosal defence strategies of the mucosa and oropharynx?

A

Endogenous flora
Epithelium and mucus
Regionalised immune system and gut homing of B and T cells
Lymphoid complexes along GI tract

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6
Q

Describe the adaptions of the epithelium and mucus

A

Mechanical barriers - cells and tight junctions
Specialised epithelial cells - goblet cells, absorptive epithelial cells, M cells, paneth cells
Antimicrobial substances
Mucins form viscous barrier

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7
Q

What are mucins?

A

Extensively glycosylated proteins

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8
Q

What are some antimicrobial substances?

A

Defensins
Lysozymes
Lactoferrin
Phospholipases

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9
Q

Where is the greater and least amount of lymphoid tissue found along the GI tract?

A

Greatest in oropharynx and terminal ileum

Least in small and large bowel

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10
Q

What are some intestinal epithelial cells?

A

Goblet cells
Epithelial cells
M cells
Paneth cells

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11
Q

What do goblet cells do?

A

Produce mucus to form physical-chemical barrier

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12
Q

What do epithelial cells do?

A

Express TLRs

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13
Q

What does surface TLR ligation lead to?

A

Tightening of epithelial junctions
Increased proliferation
Increased epithelial motility
Enhance barter function

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14
Q

What do M cells do?

A

Transport antigens to subepithelial lymphoid structures

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15
Q

What do Paneth cells produce?

A

Human defensin 5 (HD5) precursor
HD6 precursor
Trypsin which activates HD5 and HD6

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16
Q

What do Peyer’s patches contain?

A

Germinal centre for B and T cells

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17
Q

Where are Peyer’s patches located?

A

In distal ileum in areas of follicle-associated epithelium (FAE)

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18
Q

How many Peyer’s patches are there?

A

Before 30 weeks gestation, the foetus has 60

Reaches maximum of 240 by puberty

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19
Q

What are the 3 main domains of Peyer’s patches?

A

Follicular areas
Interfollicular areas
Follicle-associated epithelium

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20
Q

How does follicle-associated epithelium differ from normal epithelium?

A

Due to microvilli regularity and length

Presence of infiltrating immune cells

21
Q

What do the follicular areas of Peyer’s patches contain?

A

Proliferating B-lymphocytes
Follicular dendritic cells
Macrophages

22
Q

What do the interfollicular areas of Peyer’s patches contain?

A

Proliferating B-lymphocytes
Follicular dendritic cells
Macrophages

23
Q

How are Peyer’s patches connected to circulation?

A

By endothelial venues (from blood to PP) and lymphatic vessels (from PP to mesenteric lymph nodes)

24
Q

What are the features of M cells?

A

Small microvilli
Large cell membrane fenestrations
Trans-cellular transport of antigen
Exocytosis at basolateral membrane

25
Q

How many M cells per Peyer’s patch?

A

100 to 150

26
Q

Where are mesenteric lymph nodes located?

A

At base of mesentery

27
Q

What do mesenteric lymph nodes do?

A

Collect lymph, cells and antigens from intestinal mucosa

28
Q

What is the main site for oral tolerance induction?

A

Mesenteric lymph nodes

29
Q

Describe the IEL in the basolateral part of epithelium

A

Irregular shape
- long extensions in close contact with neighbouring epithelial cells
Occur in variable numbers along gut

30
Q

What are the 3 groups that intraepithelial T cells can be divided into?

A

TCRaB+CD8aB+
TCRaB+CD4aB+
TCRaB+CD8aa+

31
Q

What are MIC-A and MIC-B?

A

Ligands for NK cell activating receptor NKG2D

32
Q

What is T-cell differentiation influenced by?

A

Epithelial cells and dendritic cells

33
Q

What are Treg cells important in?

A

Establishing and maintaining food tolerance and class switch including TGF-B and others

34
Q

What do Th1 cells do?

A

Produce IFN-gamma

Important in killing virally infected epithelial cells

35
Q

What do Th2 cells do?

A

Induced by worm infection

Produce IL-4 and IL-113 which increase fluid secretion, mucus secretion, bowel motility and smooth muscle contraction

36
Q

What do Th17 cells do?

A

Produce IL-17 and IL-22

Cytokines interact with receptors on epithelial cells to regulate production of mucins or defensins

37
Q

What do dendritic cells do?

A

In lamina propria
Long extensions that reach through epithelium to sample contents of intestinal tube
Antigens get presented to T cells

38
Q

Describe the protection of secretory IgA against epithelial invasion

A

Cross-reactive innate-like (low affinity) and infection or vaccine induced specific (high affinity) protection

39
Q

What do pIgA and pIgM do?

A

Exert non-inflammatory effects inside and below epithelium
Neutralisation of virus or endotoxin
Antigen excretion

40
Q

Describe IgA antibody

A

IgA against food antigens provides immune exclusion
IgA weakly activates complement system
Secretion of IgA coupled to J chain depends on trans-cellular transport mechanisms

41
Q

How do activated T cells and circulating memory cells exit the lymph nodes?

A

Via efferent lymphatics
Return to circulation through thoracic duct
Reach target tissues via blood stream

42
Q

What guides effector cells to different tissues?

A

Different combinations of homing receptors

At the tissue, up regulation of respective ligand molecule is related to the situation in the tissue

43
Q

What are the inductions sites?

A

Peyer’s patches

Mesenteric lymph nodes

44
Q

What does priming in the induction sites lead to?

A

Expression of a4B7 and CCR9 (homing receptors)

45
Q

What do homing receptors do?

A

Facilitate migration from blood to effector sites

46
Q

What are the effector sites?

A

Lamina propria

Gut epithelium

47
Q

What type of cells does IEL include?

A

Treg
Th1
Th2
Th17

48
Q

Why are regulatory T-cell responses important in regard to food antigens?

A

Absorption of nutrients and inflammation are incompatible

Module 204 MSK & Immune system (44 decks)

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