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biosci S1 Pt2 > Lec 22- Infection and innate immunity > Flashcards

Lec 22- Infection and innate immunity Flashcards

1
Q

What are examples of a cellular innate response?

A

phagocytic cells
Natural killer cells

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2
Q

What are examples of a cellular adaptive immune response?

A

B and T cells

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3
Q

What is an example of a humoral adaptive immune response?

A

Antibodies

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4
Q

Which came first, innate or adaptive immunity?

A

Innate came first, has been around for 500 million years.

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5
Q

What are the three major interlinked processes that provide us with innate immunity?

A

Complement (C’)
Myeloid cells and phagocytosis (neutrophils and macrophages)
Pattern recognition receptors (PRR)

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6
Q

What are examples of a humoral innate immune response?

A

Complement
Mannose binding protein
Antimicrobial peptides
LPS binding protein
C-reactive protein

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7
Q

Does the innate response have memory?

A

No. What you have is what you were born with and will die with and the 20th response is the same as the 1st.

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8
Q

What are the three main types of pathogens?

A

Viruses
Bacteria
Protozoa and parasites

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9
Q

How many people died of the spanish flu and when was it?

A

50 million in 1918. Simple virus with only 4-5 genes.

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10
Q

Is there any smallpox left?

A

No

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11
Q

Is there a vaccine for HIV?

A

No

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12
Q

Name 6 well known viruses

A

Smallpox
polio
influenza
varicella
HIV
Sars-COV-2

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13
Q

How do viruses thrive in our body?

A

They cannot grow on their own. they take over a cell, and uses the cell’s replicatory mechanism to divide and discards the cell

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14
Q

Are viruses intracellular or extracellular pathogens?

A

Intracellular

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15
Q

What does defence rely on for viruses?

A

Relies on antibodies and cellular immunity - need to be able to distinguish infected from normal cells

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16
Q

Are bacteria intracellular or extracellular pathogens?

A

Mostly extracellular

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17
Q

How is defence mediated for bacteria?

A

primarily mediated by innate mechanisms and phagocytosis

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18
Q

What is an example of an intracellular bacterium?

A

Mycobacterium- which causes tuberculosis

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19
Q

What is the defence for protozoa and parasites?

A

They cannot be digested through phagocytosis and require direct killing by chemical mediators by specialist myeloid cells (eosinophils and basophils)

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20
Q

What is lymphoedema?

A

When the lymph fluid cannot flow back up to the heart due to a worm in the lymph nodes

21
Q

What are the features of a gram-positive bacterium?

A

they have thick peptidoglycan cell wall as a defence. Required phagocytosis and are not killed directly my complement

22
Q

Name two examples of gram-positive bacterium

A

S. aureus
S. pyogenes

23
Q

What are the features of a gram-negative bacterium?

A

Have a thin peptidoglycan cell wall. Have an outer membrane surrounding it. These bacteria can be lysed directly by complement membrane attack complex (MAC)

24
Q

What is the target for the most common form of antibiotics?

A

The cell wall (peptidoglycans)
penicillin

25
Q

What are the steps to extravasation for a neutrophil?

A
  1. activation
  2. Tethering
  3. adhesion
  4. Diapadesis
  5. chemotaxis
26
Q

What is included in the activation step of extravasation for a neutrophil?

A

Chemokines from tissue injury or inflammation activate the endothelial cells lining an adjacent capillary wall

27
Q

What is included in the tethering step of extravasation for a neutrophil?

A

Neutrophil tethers to the inside capillary wall. Mediated by selectins on endothelial cells, and SIALYL LEWIS X (sLex) which is a carbohydrate antigen on neutrophils. This makes the neutrophil roll (due to blood flow) but as if it was stuck to the endothelium due to those weak interactions.

28
Q

What is included in the Adhesion step of extravasation for a neutrophil?

A

eventually, strong binding between neutrophil integrins and ICAM-1 on the endothelium occurs
NEUTROPHIL IMMOBILISES AND FLATTENS

29
Q

What is included in the diapadesis step of extravasation for a neutrophil?

A

Neutrophil squeezes between endothelial cells into the interstitial space

30
Q

What is included in the chemotaxis step of extravasation for a neutrophil?

A

Neutrophil migrates along a chemical gradient to the site of infection

31
Q

How long does the process of extravasation for a neutrophil take, from the first point of injury

A

A matter of minutes

32
Q

How do neutrophils detect bacteria?

A

Because the bacteria has been opsonised, the chemoattractant such as C5a are being released, and the neutrophil senses this.

33
Q

What does it mean by ‘neutrophils migrate up the chemoattractant gradient’, and how can they move?

A

They are going to where concentration is highest. They move by polymerising actin filaments at their leading edge and de-polymerising those filaments at their trailing edge

34
Q

Which of the four complement receptors is the most important?

A

CR1. CR1 is the main neutrophil receptor and binds to C3b.

35
Q

What are complement receptors?

A

Myeloid cell receptors that bind activated complement components deposited on bacteria

36
Q

Cross-linking of the surface complement receptors…?

A

Initiates phagocytosis

37
Q

what are FcR?

A

Fc receptors, and they bind antibodies that are already bound to the surface of a bacteria to the cell membrane of the neutrophil

38
Q

What is the process of FcR mediated phagocytosis?

A
  1. Antibody (IgM and IgG) binds to bacterial antigens
  2. exposes the Fc region
  3. FcR binds to antibodies
  4. activates phagocytosis
  5. membrane invaginates to form a phagosome
  6. fuses with lysosome to form phagolysosome
  7. Phagolysosome acidifies and superoxides kill bacteria
39
Q

What does phagocytosis depend on?

A

Relies on recognition of the microbe

40
Q

What is the main purpose of pattern recognition receptors? (PRRs)

A

they sense signs of infection or damage, which launches a signalling cascade designed to deal with the threat

41
Q

What is a Toll-like receptor? (TLR)

A

A type of pattern recognition receptor

42
Q

What are PAMPs?

A

Pathogen associated molecular patterns. They are molecules or sequences that are only found in pathogens, that are recognised by PRRs

43
Q

what are the features of PAMPs?

A

Typically very complex (lipopolysaccharides)
Evolutionarily stable (dont change much)
stimulates ‘hey adaptive immune system? i need help’

44
Q

What is TLR4?

A

toll-like receptor 4 for lipopolysaccharide (LPS)

45
Q

LPS is a membrane component of all gram _______ bacteria

A

negative

46
Q

LPS is a pyrogen. What does this mean?

A

It causes fever when it enters the bloodstream.

47
Q

Release of LPS by gram negative bacterial infections leads to…?

A

Life threatening septic shock

48
Q

what is LPS?

A

A bacterial molecule used by PRR to sense invasion

biosci S1 Pt2 (16 decks)

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