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Immunology and Infection > Immune Evasions > Flashcards

Immune Evasions Flashcards

1
Q

S. Aureus facts

A

Can cause localised pyogenic diseases by enzymes and cytotoxins
Can cause systemic diseases by toxins (superantigens)

Anaerobic/Aerobic growth
Capsule keeping safe from phagocytosis
Catalase + Coagulase test positive

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2
Q

What is Scalded skin syndrome?

A

Superficial layers of skin peel off due to S.Aureus Exfoliative toxins A and B spread from localised area into blood

Toxin - mediated

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3
Q

What disease is Impetigo?

A

localised pus filled nodule infection, reddened skin usually on children’s face and limbs.

Pyogenic

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4
Q

What is Impetigo involving hair follicles?

A

Folliculitis

Pyogenic

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5
Q

Why can Furuncles and Carbuncles become dangerous?

A

The large, pus filled nodules can progress into deeper layers of skin and spread in blood - secondary infections

Pyogenic

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6
Q

What is frequently followed by viral infections of the respiratory tract?

A

Pneumonia - abscess formation in the lungs

Pyogenic

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7
Q

What is Endocarditis?

A

infection of endothelial heart lining - high mortality

Pyogenic

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8
Q

What is Osteomyelitis?

A

Infection / destruction of bones, usually long bones with highly vascularised areas

Pyogenic

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9
Q

What is the name of the infection of joint spaces characterised by swelling, redness, puss accumulation at joint?

A

Septic Arthritis

Pyogenic

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10
Q

what is Food poisoning?

A

Heat-stable enterotoxin contaminates food = vomiting, diarrhea, stomach cramps.

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11
Q

Why does Food poisoning rapidly get better after 24 hours?

A

Because intoxication is due to toxin on food, not bacteria growing and producing toxin in intestine

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12
Q

What is Toxin shock syndrome?

A

Localised infection of bacteria, toxin affects multiple organs. Fever, hypotension, rash. High mortality rate unless local infection managed

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13
Q

Oral therapy examples?

A

Trimethoprim, sulfamethoxazole, clindamycin, doxcycyline

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14
Q

What is Vancomycin for?

A

Drug of choice for intravenous therapy

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15
Q

What are common features bacteria share despite diversity

A 
Lipopolysaccharides (LPS) in Gram -
Lipoteichoic acid (LTA) in Gram +
Flagella
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16
Q

How does Antibody Opsonisation lead to Neutrophil activation?

A

Gradient of C3a and C5a + bacterial proteins created from area of antibody opsonisation

C5a binds C5aR
C3a binds C3aR
Endothelial cells express ICAM and so when neutrophils roll along inner surface, they adhese

Transmigration out of vessel, Priming and chemotaxis towards complement + bacterial protein componants

Activated Neutrophil then can cause phagocytosis, inflammation or degranulate

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17
Q

How does S.aureus hide its antigens?

A

Capsule on surface.

E.coli, S.Pneumonia, S.agalactiae, Spyogenes also do this

18
Q

What is SSL10?

A

S.aureus secreted protein that binds to Fc region of IgG, preventing Fc regions of neutrophils from detecting IgG on surface of s.aureus

19
Q

What is SpA?

A

S.aureus surface protein which binds to antibodies via Fc region.
preventing normal opsonisation which needs binding via Fab region.

20
Q

Other bacteria expressing surface proteins that bind to antibodies and prevent opsonisation?

A

Streptococcus dysgalactiae - Protein G binds IgG
Peptostreptococcus magnus - Protein L binds to IgG
Streptococcus agalactiae - Beta protein binds IgA

21
Q

What are proteins Sbi and Sak?

A

Sbi like Spa inhibits antibody opsonisation

Sak like SSL10 inhibits detection of antibody

22
Q

What are PRRs?

A

Pathogen recognition receptors

are proteins capable of recognising molecules frequently found in pathogens directly and can prime/activate neutrophils

23
Q

TLR receptor?

A

A PRR, detects conserved microbial structures

24
Q

CLEC receptor?

A

A PRR, detects microbial carbohydrates

25
Q

FPR receptor?

A

A PRR, detects Formylated peptides

26
Q

What is ITAM ?

A

Activatory motif on Neutrophils enhance immune cell activity so Neutrophil receptors can detect opsonised microbes through Fc receptors on antibodies or
through complement receptors

27
Q

How do immune receptors modulate function?

A 
Cytokine receptors 
Chemoattractant receptors
LAIR receptors (inhibitory - prevent wrong activation)
SIGLEC receptors. (inhibitory)
LILR receptors 
CEACAM receptors
28
Q

How does CHIPs? inhibit chemotaxis and activation

A

(Chemotaxis inhibitory protein of Staphylococcus aureus)

binds to C5aR and FPR1 (detects formylated peptides - fMLP) preventing binding of agonists C5a and formylated peptides.

Do neutrophils do not migrate and do not become activated by C5aR FPR1

29
Q

How does FLIPr and SSL5 prevent phagocytosis

A

FLIPr inhibits Fc gamma receptors - IgG
SSL5 inhibits Fc alpha receptors - IgA

prevents detection of IgG/IgA opsonised bacteria

30
Q

Which S.Aureus toxins that kill/inactivate neutrophils?

A

PVL

PSM

31
Q

Bacterial Immune Evasions?

A

Express proteins which bind to inhibitory receptors and switches off neutrophil activity.

Protein examples: S.agalactiae B protein

N.gonorrhoeae opa protein

H. pyolri Hop Q protein

E.Coli

32
Q

How to neutrophils inhibit effects of bacterial proteins?

A 
Granules have anti-microbial compounds inhibiting:
SPIN protein
S.pneumoniae SP-1749
Y pestis YOPE
P.aeruginosa EXOS protein
33
Q

What do IFN initiate?

A

Interferons initiate antiviral state: transcription of genes to block replication and activates NK cells

34
Q

How does the body remove free virus?

A

Antibody agglutination

35
Q

How can viruses evade antibody recognition?

A

Rhinovirus exists as 100s of distinct serotypes
HIV as multiple clades and quasi species
Multiple Serotypes
Antigenic drift
Antigen shift

36
Q

How are NK cells activated?

A

activated by IFN 2 and IL 12 which activate macrophages with IFN Gamma

37
Q

What do Macrophages do in response to viruses?

A

Filter viral particles from blood, inactivate opsonized viral particles.

38
Q

Which Interferon is secreted by every cell?

A

IFN-Beta

39
Q

Which IFN receptor is in all tissues?

A

IFN- alpha R

40
Q

Which cells secrete IFN - alpha

A

Plasmacytoid dendritic cells

41
Q

What produces typeII IFN Gamma?

A

Activated T and NK cells

42
Q

What is type III IFN?

A 
IFN Lambda (λ)
signals through IL28 R and IL10-Beta

receptors on epithelial surfaces

Immunology and Infection (13 decks)

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