Innate cells

Question 1

What are the different phagocytes of the innate immune system?

Answer 1

Neutrophils, macrophages and dendritic cells

Question 2

What are the different lymphocytes of the innate immune system?

Answer 2

Natural killer cells

Question 3

Distinguish phagocytes and lymphocytes in their role in the innate immune system.

Answer 3

Phagocytes kill off extracellular pathogens

Lymphocytes kill off intracellular pathogens

Question 4

What process do phagocytes used to destroy pathogens?

Answer 4

Phagocytosis

Question 5

What process do lymphocytes of the innate immune system use to destroy pathogens?

Answer 5

Initiate apoptosis in infected cells

Question 6

Describe, briefly, the process of phagocytosis.

Answer 6

Phagocyte binds to a pathogen, and endocytoses it into a vesicle, called a phagosome,
The phagosome then fuses with the lysosome, which dumps acid and enzyme contents to cause degradation of the pathogen

Question 7

What does the lysosome contain to kill most ingested pathogens?

Answer 7

Acid and enzymes

Question 8

Where does the pathogen actually get killed in the phagocyte?

Answer 8

Phago-lysosome

Question 9

What receptors are expressed on the phagocyte cell surface?

Answer 9

PRRs - pattern recognition receptors

Question 10

What antigens are expressed on pathogens that are recognized by phagocytes?

Answer 10

PAMPs - pathogen-assocaited molecular patterns

Question 11

Does a phagocyte phagocytose only one pathogen at a time?

Answer 11

No, a phagocyte has many different PRRs and can simultaneously phagocytose many extracellular pathogens.

Question 12

What are the key characteristics of PAMPs?

Answer 12

Only expressed by microbes

Low mutation rate/highly conserved since these are critical for pathogen survival

Question 13

One PRR only binds to one PAMP (T or F)?

Answer 13

False. The same PRR can bind multiple PAMPs

Question 14

Why is it important that a single PRR be able to bind many different PAMPs?

Answer 14

because there is a limited number of PRRs

Question 15

What is the importance of innate immunity?

Answer 15

Allows efficient recognition of pathogens

Very effective at destroying the majority of pathogens, early

Question 16

PRRs recognize host cells in the healthy condition (T or F).

Answer 16

False. PRRs ONLY recognize and bind to pathogens

Question 17

What are the main phagocytes?

Answer 17

Neutrophils, macrophages, immature dendritic cell

Question 18

Where are neutrophils located?

Answer 18

Circulate in the blood

Question 19

Describe the characteristic of neutrophils.

Answer 19

Circulate in the blood
most abundant leukocyte in the blood
exit blood and rapidly enter into infected tissue
rapidly differentiate from myeloid progenitors in response to infection
short lived

Question 20

What is pus primarily composed of?

Answer 20

dead neutrophils and cellular debris

Question 21

What is neutropenia?

Answer 21

Low neutrophil count

Question 22

People with neutropenia are at high risk for what?

Answer 22

Serious bacterial infections

Question 23

Why are people with neutropenia not more susceptible to viral infection?

Answer 23

Neutrophils are only involved in destroying extracellular pathogens - viruses are obligate intracellular parasites, and thus not affected

Question 24

What is important when treating neutropenia?

Answer 24

To respond quickly to early symptoms to prevent bacteria sepsis and septic shock

Question 25

Describe the key characteristics of macrophages.

Answer 25

Located in the tissues (most reside below epithelial cells)
Arise from monocytes that enter the tissues
Have a role in adaptive immunity

Question 26

Where do monocytes circulate?

Answer 26

The blood

Question 27

Describe the key characteristics of dendritic cells.

Answer 27

immature dendritic cells circualte in the blood and reside in the tissues (below or among epithelial cells)

Question 28

What does the dendritic cell role and function depend on?

Answer 28

Maturation state

Question 29

What do immature phagocytes do, vs mature ones?

Answer 29

Immature phagocytes have a role in innate immunity

mature ones initiate adaptive immunity

Question 30

Which phagocytes are the first responders to a pathogen?

Answer 30

Dendritic cells and macrophages (As they are located in the tissues)

Question 31

What are the key properties of NK cells?

Answer 31

Circulate in the blood (need to enter into infected tissue)
Kill intracellular viruses and cancer cells
Have cytoplasmic granules with toxic enzymes

Question 32

How do NK cells kill virus-infected cells?

Answer 32

NK cell binds to virus infected cell, activating it and causing it to release toxic enzymes into the infected cell.
This leads to DNA damage for both the infected cell and virus, leading to apoptosis and blocking of viral replication.

Question 33

NK cells provide an early response to what?

Answer 33

Intracellular viruses

Question 34

Why do NK cells usually fail to eradicate intracellular bacteria?

Answer 34

These are bacteria that have been phagocytosed, but do not die from the process. Instead, T cells will destroy the intracellular bacteria - NK cells are better for virus infected cells.

Question 35

How can intracellular bacteria get around phagocytosis?

Answer 35

Live in the phagosome by preventing fusion with the lysosome
Live in the phagolysosome by being resistant to acid and enzymes
Escape the phagosome and replicate in the cytoplasm