Innate Immunity

Question 1

What is the innate immune system?

Answer 1

It is the non-adaptive immune system to defend the host against pathogens. It exists in the germ line and does not undergo any genetic rearrangements.

Question 2

What are the main cells of the innate immune system?

Answer 2

Phagocytes

Question 3

What are the two major types of phagocytes found in the innate immune system?

Answer 3

Macrophages

Neutrophils

Question 4

What are some of the characteristics of macrophages?

Answer 4

• are long-lived leukocytes.
• are widely distributed in normal tissues.
• are often the first cell to encounter a pathogen.
• represent the mature form of circulating monocytes.
• increase in number at sites of injury or infection.

Question 5

What are some of the characteristics of neutrophils?

Answer 5

• are short-lived circulating leukocytes.
• are the most abundant type of white cell in the circulation.
• are rarely found in normal tissues.
• can be quickly recruited to sites of injury or infection.

Question 6

What does it mean if neutrophils are seen in high amounts in tissues?

Answer 6

There is likely some sort of problem present in the tissue

Question 7

What is opsonization?

Answer 7

Opsonization is the coating of particles by molecules that enhance recognition by phagocytes.

Adaptive immunity can opsonize pathogens with antibodies. The innate immune system can opsonize pathogens with proteins of the complement system.

Question 8

What is the function of cytokines and what innate cells produce them?

Answer 8

Macrophages make them to act on cells to program them for microbial combat

Question 9

What is the function of chemokines and what innate cells produce them?

Answer 9

Macrophages make them with chemoattractant properties to recruit leukocytes to sites of infection

Question 10

What is the function of lipid mediators?

Answer 10

They have a similar function to cytokines in reprogramming cells

Question 11

What are cell surface PRRs?

Answer 11

PAMP recognition receptors

Question 12

Where are PRRs highly expressed?

Answer 12

Macrophages and dendritic cells

Question 13

What is the function of TOLL like receptors?

Answer 13

Transmembrane and sense extracellular

infection like bacteria

Question 14

What is the function of C-type lectin receptors?

Answer 14

Transmembrane and sense sugars for fungal infections

Question 15

What is the function of Rig-I like receptors?

Answer 15

Cytosolic and recognize viral RNA

Question 16

What is the function of NOD like receptors?

Answer 16

Cytosolic and recognize bacteria and viruses that enter the cell

Question 17

What is inflammation?

Answer 17

Inflammation is a general term for the accumulation of fluid, plasma proteins and white blood cells that occurs in tissue subjected to injury, infectious agents, or immune responses.

Question 18

What are the effects and purposes for inflammation?

Answer 18

Inflammation is fundamentally protective and is intended to destroy or wall off the offending agent.

It is interwoven with tissue repair but can be destructive if it goes on too long.

Question 19

What are the 3 key events in inflammation?

Answer 19

• Alteration of blood flow
• Increased vascular permeability
• Infiltration of WBCs

Question 20

What is alteration of blood flow in inflammation?

Answer 20

Vasodilation will occur and increased blood flow to the tissue will result (calor, rubor, dolor)

Question 21

What is the increased vascular permeability in inflammation?

Answer 21

Endothelial cells contract and allow for the leakage of more serum into the tissue space (tumor)

Question 22

What is the infiltration of WBCs in inflammation?

Answer 22

Neutrophils move in early on then macrophages and lymphocytes come to the site last.

Question 23

What activates the innate immune system and how fast is this response?

Answer 23

It occurs within minutes and is activated by Pattern recognition receptors (PRRs) on DC or macrophages.

Question 24

What are the various types of PRRs?

Answer 24

TLR
CLR
NLR
RLR

Question 25

What does the TLR-4 PRR specifically respond to?

Answer 25

LPS bacteria

Question 26

What happens when a PRR is activated?

Answer 26

Common characteristics of TLR activation are downstream signaling pathways in phagocytes/DC.

The final common path for pro-inflammatory activation is NF-kB. Activation of transcription factor NF-kB activates genes encoding pro-inflammatory cytokines

Question 27

What is the function of dendritic cells in the innate immune system?

Answer 27

They roam around the body and phagocytize to become antigen presenting cells. This will direct the type of adaptive response that occurs.

Question 28

What is the function of the natural killer cells in the innate immune system?

Answer 28

Lymphocytes in the blood that can directly kill the target infected cell or cancerous cell

Question 29

What are NK T cells?

Answer 29

They are not natural killer cells and are instead a subset of T cells as they have a T cell receptor that is restricted to glycolipid (instead of peptide) antigens.

Question 30

What are gamma/delta lymphocytes?

Answer 30

They recognize small molecule phosphoantigens which are metabolic intermediates in lipid biosynthesis in bacterial but not in mammals under normal circumstances.

Question 31

How can the innate system have “memory?”

Answer 31

The innate system can be trained to remember an infection so that it can respond more strongly and quickly during secondary infections.

This occurs via epigenetic changes that result in perpetual activation of genes necessary to support the increased metabolic activity of these trained cells.

Question 32

What are PMNs?

Answer 32

Neutrophils

Question 33

What is cellular immunity?

Answer 33

It is a process during which host effector cells are induced to kill pathogens directly

Question 34

What is humoral immunity?

Answer 34

It is a process that utilizes the production of antigen specific antibody immunoglobulins to neutralize or target pathogens for elimination.