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MICR2221 - Medical Immunology > L13 - Mucosal Immunity > Flashcards

L13 - Mucosal Immunity Flashcards

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USMLE® Step 1 flashcards
1
Q

Essential function of mucosal surfaces?

A

Gas exchange
Food absorption
Sensory activities
Reproduction

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2
Q

What are the mucosal surfaces for entry of pathogens?

A

Mouth & respiratory contract

Gastrointestinal tract

Reproductive tract

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3
Q

3 functions of the epithelium?

A

Lines mucosal surfaces defining border

Defends from invasion

selectively transports components essential for life to lamina/circulation

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4
Q

What are the 2 ways that mucosal tissue is defined?

A

Scattered - lymphocytes dotted around

Organised - B cell and T cell areas concentrated in 1 area - drain the lymph nodes

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5
Q

Anatomical features of the mucosal immune system?

A

Interactions between mucosal epithelia and lymphoid tissues

discrete compartments of diffuse lymphoid tissue and organised structures e.g. tonsils

specialised antigen-uptake mechanisms e.g. M cells in Peyer’s patches

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6
Q

Effector mechanisms of the mucosal immune system?

A

Presence of distinctive microbiota

Secretory IgA antibodies

activated ‘natural’ effector T cells present

Activated T cells predominate even without infection

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7
Q

Immunoregulatory environment of the mucosal immune system?

A

Active downregulation of immune response

Inhibitory macrophages & tolerance-inducing DCs

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8
Q

The 4 cells that stem cells differentiation in mucosal tissue leads to?

A

Enterocytes/colonocytes
Paneth cells
Goblet cells
Enteroendocrine cells

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9
Q

function of enterocytes/colonocytes?

A

absorptive

AMPs production

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10
Q

function of paneth cells?

A

AMPs

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11
Q

function of goblet cells?

A

mucus secretion - lubricate food and prevent bacteria binding

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12
Q

function of enteroendocrine cells?

A

neurohumoral factors secretion - enzymes

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13
Q

What are M cells?

A

sample environment and phagocytose pathogens

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14
Q

Antimicrobial protein families in intestine and skin?

A

REG3y - bind onto carbs

BD1/2/3/4 - produced by sebaceous gland

RNases

Lactoferrin - ferrous ions

Calprotectin - binds Ca ions

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15
Q

What is the dominant class of Ab on mucosal surfaces?

A

IgA
IgA1 - lung
IgA2 - colon

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16
Q

Major function of IgA?

A

IMMUNE EXCLUSION

IgA adsorb on the mucus layer - interactions between carbohydrates

IgA do NOT activate complement classical pathway - does NOT promote inflammation

17
Q

What are IgA resistant to?

A

protease

18
Q

What are the immune cells of the mucosa?

A

Intraepithelial lymphocytes (IELs)

19
Q

What do IELs recognise?

A

epithelial cells expressing abnormal phenotypes resulting from stress/infection

20
Q

What are ILCs?

A

Innate Lymphoid cells

21
Q

Group 1 ILCs?

A

ILC1
NK cells
IFNy
similar to Th1

22
Q

Group 2 ILCs?

A

ILC2
Trigger soluble antibody response
similar to Th2

23
Q

Group 3 ILCs?

A

ILC3
Inflammatory response & epithelial type immunity
similar to Th17 & Th22

24
Q

What samples the mucosal compartments?

A

Distinct DCs e.g. CD103+

25
Q

What is MadCAM?

A

on vasculatare of all mucosa

Gut homing lymphocytes

26
Q

Why are host-commensal interactions needed in the gut?

A

help to digest food

responsible for extraction & synthesis of nutrients

compete with pathogens

inhibit pathway that is required for pathogen uptake

27
Q

What gut infection can arise when antibiotics are used?

A

Clostridium difficile

altered gut environment and pathological inflammation

28
Q

What is happy equilibrium “physiological inflammation”?

A

Commensal bacteria constantly triggering slight inflammation

important in calming the immune response

29
Q

How does salmonella cause infection?

A

kill M cells - infect macrophages and epithelial cells

invade luminal surface of epithelial cells

enter phagocytes cells that are sampling gut luminal contents

30
Q

How does shigella cause infection?

A

physically kills M cells

invade basal surface of epithelial cells and spread

cell-wall peptides binds NOD1 - activate NFkB pathway

activated epithelium secretes CXCL8 - recruits neutrophils

31
Q

What does shiga toxin do?

A

inhibit translation

32
Q

What does Clostridium difficile toxin A do?

A

inactivates GTPase

33
Q

What does rotavirus NSP4 do?

A

disrupts tight junctions

34
Q

What response do helminth infections provoke?

A

Th2

IL13 - epithelial cell repair

M2 macrophages activated

Driver B cells to produce IgE

IL5 recruits eosinophils

IL3/IL9 mast cell recruitment

35
Q

Aberrant mucosal immunity?

A

Crohn’s - NOD2, Atg16L1 - phagoctyoses intracellular bacteria

Coeliac - HLA-DQ2 - binds gliadin

C. difficile

MICR2221 - Medical Immunology (16 decks)

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