Immune Evasions

Question 1

S. Aureus facts

Answer 1

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

Question 2

What is Scalded skin syndrome?

Answer 2

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

Toxin - mediated

Question 3

What disease is Impetigo?

Answer 3

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

Pyogenic

Question 4

What is Impetigo involving hair follicles?

Answer 4

Folliculitis

Pyogenic

Question 5

Why can Furuncles and Carbuncles become dangerous?

Answer 5

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

Pyogenic

Question 6

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

Answer 6

Pneumonia - abscess formation in the lungs

Pyogenic

Question 7

What is Endocarditis?

Answer 7

infection of endothelial heart lining - high mortality

Pyogenic

Question 8

What is Osteomyelitis?

Answer 8

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

Pyogenic

Question 9

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

Answer 9

Septic Arthritis

Pyogenic

Question 10

what is Food poisoning?

Answer 10

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

Question 11

Why does Food poisoning rapidly get better after 24 hours?

Answer 11

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

Question 12

What is Toxin shock syndrome?

Answer 12

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

Question 13

Oral therapy examples?

Answer 13

Trimethoprim, sulfamethoxazole, clindamycin, doxcycyline

Question 14

What is Vancomycin for?

Answer 14

Drug of choice for intravenous therapy

Question 15

What are common features bacteria share despite diversity

Answer 15

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

Question 16

How does Antibody Opsonisation lead to Neutrophil activation?

Answer 16

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

Question 17

How does S.aureus hide its antigens?

Answer 17

Capsule on surface.

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

Question 18

What is SSL10?

Answer 18

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

Question 19

What is SpA?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

What are proteins Sbi and Sak?

Answer 21

Sbi like Spa inhibits antibody opsonisation

Sak like SSL10 inhibits detection of antibody

Question 22

What are PRRs?

Answer 22

Pathogen recognition receptors

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

Question 23

TLR receptor?

Answer 23

A PRR, detects conserved microbial structures

Question 24

CLEC receptor?

Answer 24

A PRR, detects microbial carbohydrates

Question 25

FPR receptor?

Answer 25

A PRR, detects Formylated peptides

Question 26

What is ITAM ?

Answer 26

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

Question 27

How do immune receptors modulate function?

Answer 27

``` Cytokine receptors Chemoattractant receptors LAIR receptors (inhibitory - prevent wrong activation) SIGLEC receptors. (inhibitory) LILR receptors CEACAM receptors ```

Question 28

How does CHIPs? inhibit chemotaxis and activation

Answer 28

(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

Question 29

How does FLIPr and SSL5 prevent phagocytosis

Answer 29

FLIPr inhibits Fc gamma receptors - IgG SSL5 inhibits Fc alpha receptors - IgA prevents detection of IgG/IgA opsonised bacteria

Question 30

Which S.Aureus toxins that kill/inactivate neutrophils?

Answer 30

PVL | PSM

Question 31

Bacterial Immune Evasions?

Answer 31

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

Question 32

How to neutrophils inhibit effects of bacterial proteins?

Answer 32

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

Question 33

What do IFN initiate?

Answer 33

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

Question 34

How does the body remove free virus?

Answer 34

Antibody agglutination

Question 35

How can viruses evade antibody recognition?

Answer 35

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

Question 36

How are NK cells activated?

Answer 36

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

Question 37

What do Macrophages do in response to viruses?

Answer 37

Filter viral particles from blood, inactivate opsonized viral particles.

Question 38

Which Interferon is secreted by every cell?

Answer 38

IFN-Beta

Question 39

Which IFN receptor is in all tissues?

Answer 39

IFN- alpha R

Question 40

Which cells secrete IFN - alpha

Answer 40

Plasmacytoid dendritic cells

Question 41

What produces typeII IFN Gamma?

Answer 41

Activated T and NK cells

Question 42

What is type III IFN?

Answer 42

``` IFN Lambda (λ) signals through IL28 R and IL10-Beta ``` receptors on epithelial surfaces