5- Phagocytosis

Question 1

What is phagocytosis?

Answer 1

The ability of some cells to ingest foreign particles, literally “eating by cells”

Question 2

What are the two ‘professional phagocytes’ and briefly describe their roles.

Answer 2

Neutrophils: first to accumulate around the invaders and initiate the phagocytic process- suicide bombers

Macrophages: migrate to the tissue site and initiate phagocytosis- serial killers

Question 3

List the steps of phagocytosis and briefly describe each.

Answer 3

1) Chemotaxis: delivery of phagocytic cells to the site of infection
2) Adherance: Phagocytic adherence to the target
3) Ingestion: Engulfment of the target particle
4) Destruction: Intracellular killing and digestion of the target

** Egestion only in the case of macrophages

Question 4

What are the 4 components stored in primary granules?

Answer 4

1) Hydrolases
2) Lysozyme
3) Defensins
4) Myeloperoxidase

Question 5

What is the role of hydrolases in primary granules?

Answer 5

Breaks covalent bonds by adding water, important for degrading dead bacteria or dead tissues

Question 6

What is the role of lysozyme in primary granules?

Answer 6

Breaks down peptidoglycan in gram-positive bacteria, found in many secretions of the body

Question 7

What is the role of defensins in primary granules?

Answer 7

Small cationic proteins that kill bacteria, especially gram-positive
Aka antimicrobial peptides
Form a barrel shape around the bacteria and punches holes in it

Question 8

What is the role of myeloperoxidase in primary granules?

Answer 8

An enzyme that has an important role in the oxygen mediated killing mechanism

Question 9

What makes up the contents stored in secondary granules?

Answer 9

1) Lysozyme
2) Lactoferrin
3) Collagenase

Question 10

What is the role of lysozyme in secondary granules?

Answer 10

Breaks down peptidoglycan in gram-positive bacteria, found in many secretions of the body

Question 11

What is the role of lactoferrin in secondary granules?

Answer 11

chelates iron- bacteria need iron for survival

Question 12

What is the role of collagenase in secondary granules?

Answer 12

degrades connective tissue, so it can move through to the site of inflammation

Question 13

What is opsonization?

Answer 13

Coating of positively charged material on a pathogen so a neutrophil can bind to and kill it
Both pathogens and neutrophils are negatively charged, so they naturally repel each other without opsonization

Question 14

What is a phagosome?

Answer 14

Membrane-bound vesicle containing the ingested microbe or material in the process of phagocytosis

Question 15

What are the two neutrophil membrane receptors that ard important in phagocytosis?

Answer 15

Fc receptors- bind antibody that is bound to an antigen, especially IgG antibody

C3b receptors- bind to C3b when it is coating bacteria, etc

Question 16

Once neutrophils bind to opsonized material, it is readily engulfed, forming a ________.

Answer 16

Phagosome

Question 17

What is a phagolysosome

Answer 17

Formed when the membranes of the phagosome and lysosome actually fuse resulting in a digestive vacuole called the phagolysosome, other lysosomes will continue to fuse as well

Question 18

Where does the killing and digestion of the engulfed microbe take place?

Answer 18

Phagolysosome

Question 19

What is the most potent killing mechanism of a neutrophil?

Answer 19

Oxygen mediated killing mechanism

Question 20

What are the killing products used in the oxygen mediated killing mechanism?

Answer 20

Hypochlorite
Hydrogen peroxide
Aldehydes
Oxygen radicals

Question 21

What is the fate of neutrophils after killing a pathogen?

Answer 21

Neutrophils die and lyse after extended phagocytosis, killing, and digestion of bacterial cells

***This makes up the main component of pus

Question 22

What is the fate of macrophages after killing a pathogen?

Answer 22

Macrophages egest (discharge) digested debris and allow insertion of microbial antigenic components into the plasma membrane for presentation to lymphocytes in the immunological response

Question 22

What is the difference between M1 and M2 macrophages?

Answer 22

M1- phagocytic cells like neutrophils
M2- clean up the mess

Question 22

What are the first cells attracted to sites of inflammation?

Answer 22

Neutrophils

Question 23

Cytokines activate _________ _________ _________ so that neutrophils in the bloodstream will stop, attach, and then migrate toward the sites of microbial invasion and tissue damage

Answer 23

vascular endothelial cells

Question 24

_________ bind, phagocytose, and kill invading microorganisms.

Answer 24

Neutrophils

Question 25

Microorganisms must usually be __________ before the can be efficiently ingested and killed.

Answer 25

opsonized

Question 26

What are the two most effective opsonins?

Answer 26

antibodies and complement

Question 27

Ingested microorganisms are killed by potent oxidants through a process called the ______ _______, by antibacterial proteins called _______ and by _______ _______.

Answer 27

Respiratory burst
defensins
lytic enzymes

Question 28

Can neutrophils undertake multiple phagocytosis?

Answer 28

no

Question 29

_______ migrate to sites of inflammation after neutrophils.

Answer 29

Macrophages
they eat and kill any surviving microbial invaders

Question 30

Macrophages also eat dead and dying neutrophils thus preventing what?

Answer 30

Damage caused by escaping neutrophil enzymes

Question 31

Which cells begin the healing process in damaged tissues?

Answer 31

Macrophages

Question 32

Macrophages are essential antigen-presenting cells for adaptive or innate immune system?

Answer 32

Adaptive