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1. Immunology > Phagocytosis and Opsonisation > Flashcards

Phagocytosis and Opsonisation Flashcards

1
Q

What is pinocytosis?

A

A mechanism by which cells can “drink” liquid from outside

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2
Q

What cells use pinocytosis

A

All cells

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3
Q

List the four phagocytes.

A

Neutrophils

Monocytes

Macrophages

Dendritic cells

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4
Q

Explain how phagocytosis occurs.

A

The target adheres to the surface of the phagocyte

The phagocyte engulfs the microbe and encloses it within a membrane-bound vesicle known as a phagosome

The phagosome fuses with a lysosome, an organelle that contains digestive enzymes

Whatever indigestible material remains is exocytosed

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5
Q

What engulfs the microbe during phagocytosis?

A

A phagosome engulfs the microbe

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6
Q

What is the phagosome?

A

a membrane-bound vesicle

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7
Q

What does the phagosome fuse with?

A

A lysosome

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8
Q

What is a lysosome?

A

An organelle that contains digestive enzymes

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9
Q

What digests captured materials in the phagosome?

A

Lysosomal enzymes

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10
Q

What happens to the materials that are digested in a phagosome?

A

They are released from the cell

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11
Q

What is the resulting organelle called when a phagosome fuses with a lysosome?

A

Phagolysosome

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12
Q

What are the six different ways that a phagolysosome can kill microbes?

A

Acidification

Toxic oxygen-derived products

Toxic nitrogen oxides

Antimicrobial peptides

Enzymes

Competitors

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13
Q

Name some of the toxic oxygen-derived products used to kill microbes during phagocytosis.
(2)

A

Hydrogen peroxide (H2O2)

Hydroxyl Radical (OH.)

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14
Q

Name a toxic nitrogen oxide that can be used to kill microbes during phagocytosis.

A

Nitric oxide (NO)

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15
Q

Name two antimicrobial peptides used to kill microbes during phagocytosis.

A

Defensins

Cationic proteins

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16
Q

Name three enzymes used to kill microbes during phagocytosis.

A

NADPH-dependent oxidases

Lysozyme

Acid hydrolases

17
Q

What does NADPH-dependent oxidases do?

A

It generates toxic oxygen derivatives

18
Q

What does lysozyme do?

A

Dissolves cell walls of some Gram-positive bacteria

19
Q

What does acid hydrolases do?

A

Further digests bacteria

20
Q

Phagocytes express receptors on their cell surfaces for what five things.

A

Carbohydrates

Glycans

LPS

Complement components

Antibodies

21
Q

Give an example of a carbohydrate found in bacteria.

A

Mannose is found in bacterial cell walls

22
Q

Give an example of a glycans found in bacteria.

A

Peptidoglycan in bacterial cell walls

23
Q

How do neutrophils move towards bacteria?

3

A

Neutrophils sense the presence of bacterial products

Neutrophils move towards them along a gradient of increasing concentration

This is called chemotaxis

24
Q

Where is there a large reserve of neutrophils?

A

In the bone marrow

25
Q

Describe how a neutrophil carries out its work.

4

A

Neutrophils leave their reserves in bone marrow when they are needed to fight infection

Neutrophils travel to and enter the infected tissue

Neutrophils engulf and kill bacteria

The neutrophils die in the tissue and are engulfed and degraded by macrophages

26
Q

What cells engulf and degrade neutrophils?

A

Macrophages

27
Q

What is opsonisation?

A

A process that greatly enhances phagocytosis where components of the immune system found in the serum make the target more attractive for phagocytosis

28
Q

Describe how opsonisation works.

4

A

The surface of an invader is marker by proteins such as:

Activated complement components (part of the innate system)

Antibodies (part of the adaptive immune response)

Phagocytes have receptors that can bind to opsonised particles

29
Q

What two things can be used to mark invadors?

A

Complement components

Antibodies

30
Q

Explain how opsonisation by complement works.

A

Complement proteins in the serum are activated by the initiation of an immune response

Some of these proteins act as opsonins which facilitate receptor-mediated endocytosis of pathogens

31
Q

What are opsonins?

A

Proteins that engage with complement receptors on phagocytes

32
Q

What is endocytosis?

A

The taking in of matter by a living cell by pinching in of its membrane to form a vesicle

33
Q

What are antibodies?

A

Y-shaped protein molecules produced by B cells that can identify and
neutralise pathogens

34
Q

Explain how opsonisation by antibodies works.

A

Antibodies mark a pathogen for phagocytosis

1. Immunology (9 decks)

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