Innate Immune System

Question 1

Overview of innate immune system

Answer 1

Provides a local and generalised response to infection with a pathogen

Has mechanisms for recognising and destroying pathogens that do not require recognition of specific antigens

Question 2

Components of the innate immune system

Answer 2

Macrophages (from monocytes)
Neutrophils
Interferons
Natural Killer cells

Question 3

PAMPs

Answer 3

Pathogen associated molecular patterns (PAMPs)

Various substances that are unique to pathogens such as:

• Double stranded RNA
• Unmethylated DNA (from bacteria)
• Mannose-containing carbohydrates (from bacteria)
• Lipopolysaccharide (from bacteria cell walls)

Question 4

Cytokines

Answer 4

Proteins that act like local hormones - send signals and stimulate responses

Question 5

TLRs

Answer 5

Toll like receptors
Receptors on cells of the innate immune system (especially macrophages)
== Allow them to recognise PAMPs

Question 6

Opsonins

Answer 6

Any molecule that binds to a pathogen and signals to phagocytes to act on said pathogen

Question 7

Macrophage general response to pathogen

Answer 7

TLR bind to PAMPs:

1) Phagocytosis
2) Cytokine release - causing inflammation
3) Interferon release - preventing viral entry and replication in cells

Question 8

Which cells can phagocytose?

Answer 8

Macrophages, neutrophils and to a lesser extent eosinophils are responsible for phagocytosis

Question 9

4 stages of phagocytosis

Answer 9

1) attachment
2) ingestion
3) killing
4) degradation

Question 10

Cytokines released by macrophages:

Answer 10

Interleukins
Colony-stimulating factor
Tumor-necrosis factor
Growth factor
Chemokine

Question 11

Cytokine release leads to inflammation - which helps the innate immune system by:

Answer 11

• Actives more macrophages
• Recruiting monocytes that differentiate into macrophages when they enter the tissue
• Recruits and activates neutrophils
• Recruits and activates natural killer cells
• Brings opsonins that help macrophages and neutrophils recognise and phagocytose pathogens

Question 12

Which cells produce interferons?

Answer 12

Macrophages
lymphocytes (particularly natural killer cells)
Endothelial cells
Epithelial cells

Question 13

Interferons act by:

Answer 13

Blocking viral entry into cells

Blocking viral replication inside of cells

Activating macrophages and natural killer cells

Question 14

Natural killer cells:

Answer 14

Types of lymphocytes that are not specific to one antigen (unlike T/B-Cells)

They can recognise infected or abnormal (tumour/cancer) cells without requiring MHC or specific antigen receptors

Stimulated by Interleukin -2/-12 (cytokine from activated macrophages)

They have 2 functions:
-1) KILLING CELL: (apoptosis/lysis)
They spray target with cytokines that either stimulate apoptosis (cell death) in the cell [killing the virus inside] or create a hole in the cell membrane causing cell lysis.
-2) Secretes interferon-gamma (IFN-γ), a cytokine that further activates macrophages.