4.1.1 Phagocytosis Mechanism

Question 1

First stage?

Answer 1

The phagocyte is attracted by chemicals that are produced by the pathogen, eg cytokines; phagocytes only attack foreign cells

Question 2

What happens when organ transplants are rejected?

Answer 2

Phagocytes reject the foreign cells due to their antigens

Question 3

Stage 2?

Answer 3

The phagocyte recognises the pathogen as non-self and binds to it

Question 4

Third stage?

Answer 4

The phagocyte engulfs the pathogen to form a phagosome, then lysosomes move towards the phagosome and combine with it to form phagolysomes

Question 5

Fourth stage?

Answer 5

In the phagolysosome, hydrolytic enzymes digest the pathogen

Question 6

Stage five?

Answer 6

The digested pathogen’s antigens combine with major histocompatibility complexes (MHC) in the cytoplasm

Question 7

Stage 6?

Answer 7

The MHC / antigen complex is displayed on the phagocytic membrane, making an antigen presenting cell

Question 8

Neutrophils complete…

Answer 8

Stages 1-4, in around 10 minutes

Question 9

Macrophages complete…

Answer 9

Steps 1-6, taking longer at they make MHC

Question 10

Antigen presenting cells trigger…

Answer 10

The specific immune response

Question 11

Viral interface?

Answer 11

A group of signalling proteins made by infected host cells- interferons stimulate nearby cells to heighten their anti-viral defences

Question 12

Opsonins?

Answer 12

Chemicals that attach to pathogen’s exteriors to make them recognisable to phagocytes; phagocytes have opsonin receptors on their surfaces, which bind to opsonins; eg immunoglobulin E and H

Question 13

Cytokines?

Answer 13

Emitted by phagocytes after engulfing pathogens; cell signalling molecule that alert other phagocytes to the presence of pathogens; inflammatory response