Chemotaxis And Phagocytosis

Question 1

Who discovered phagocytosis

Answer 1

Metchnikoff

Question 2

What is chemotaxis?

Answer 2

A process that drives phagocytes to the inflammed tissue - as they respond to a chemical gradient of a certain chemical (chemotactic gradient)

Question 3

What are the potential origins of chemoattractants?

Answer 3

• substances generated by a pathogen
• substances released from dying tissue
• endogenous proteins involved in the control of infection (e.g. Complement components)

Question 4

Once the phagocyte has reached the pathogen, what are the mechanisms to eliminate it?

Answer 4

Phagocytosis and intracellular killing

Question 5

Name the steps involved in phagocytosis

Answer 5

• recognition and attachment
• engulfment
• killing and degradation

Question 6

Phagocytosis: which receptors does recognition and attachment occur though?

Answer 6

Through mannose receptors, scavenger receptors and receptors for various opsonins such as IgGs

Question 7

Phagocytosis: discuss engulfment

Answer 7

There is the formation of a phagosome which then fuses with a lysosome

Question 8

Phagocytosis: Describe how the killing and degradation phase occurs

Answer 8

ROS produced within the lysosome and other substances in leukocyte granules such as elastase, defensins, lysozyme and lactoferrin are responsible for the killing and degradation of the pathogen

Question 9

Explain what happens after phagocytosis occurs but the bacteria kills the phagocyte

Answer 9

The infection is aggrivated, as the living bacteria and dead phagocytes add to the inflammatory reaction

Question 10

What happens to neutrophils after the resolution of infections?

Answer 10

They undergo apoptosis, and are engulfed by macrophages