Immunology 1 - Intro to Immunology

Question 1

Explain the importance of immunology for human health

Answer 1

• Failure of the immune system results in disease (eg. SIDS)
• Identifies harmful pathogens by identifying self and non-self
• Must be a rapid immune response as the pathogen replicates quickly and there are so many

Question 2

What are the two basic strategies cells use to recognise pathogens?

Answer 2

• Strategy 1 (recognition of molecular pathogens, which is germ line encoded)
• Strategy 2 (recognition of the precise structure of the antigen, generated by random gene recombination)

Question 3

What are the advantages and disadvantages of strategy 1?

Answer 3

Advantages
- Many cells express the same receptor, so the response is rapid.

Disadvantages
- Receptors are not present for all pathogens

Question 4

What are the advantages and disadvantages of strategy 2?

Answer 4

Advantages
- Huge receptor diversity, can potentially recognise all structures

Disadvantages
- Expansion is slow and must occur before there is an effective response, and there is a potential for autoimmunity due to random generation of receptors.

Question 5

What are the two types of pattern recognition receptors (PRRs) used in strategy 1?

Answer 5

• PAMPs (pathogen-associated molecular patterns)

- DAMPs (damage-associated molecular patterns recognise damaged cells)

Question 6

List some examples of PAMPs

Answer 6

• Flagellin
• Peptidoglycans
• LPS (lipopolysaccharides)
• Glycoproteins

Question 7

List some examples of DAMPs

Answer 7

• Nuclear components
• Extracellular ATP
• Heat shock proteins
• Fragments from injury (eg. Collagens/fibronectins)

Question 8

What type of cells does strategy 2 use? How do they work?

Answer 8

• B cells have a membrane bound antibody that binds to intact antigens
• T cells bind to processed antigen fragments at cell surfaces with T cell receptors (TCR).
• Antibodies bind to specific sites on antigens (epitopes)
• Each clone of B or T cells has a unique receptor, with many displayed on the cell surface.

Question 9

What is the difference between innate and adaptive immunity?

Answer 9

• Innate uses strategy 1, adaptive uses strategy 2
• Innate is independent of previous exposure, adaptive is dependent on exposure.
• Innate depends on preformed components so is faster, adaptive depends on clonal selection

Question 10

What does the innate immune response do?

Answer 10

• Destroys invading Nucleic acids in the cytoplasm
• Activates inflammatory pathways and recruits immune cells
• Buys time for adaptive immunity and directs the correct response

Question 11

What types of immunity make up the adaptive immunity?

Answer 11

• Cellular (T and B cells - lymphocytes)

- Humoral (antibodies)

Question 12

What are the main components of the innate response?

Answer 12

• Neutrophils, macrophages & eosinophils
• Acute-phase proteins, cytokines, compliment
• Cross over: basophils, dendritic cells, natural killer cells

Question 13

What are the main components of the adaptive response

Answer 13

• T lymphocytes, B lymphocytes
• Cytokines, antibodies
• Cross over: basophils, dendritic cells, natural killer cells

Question 14

How is clonal diversity generated in lymphocytes?

Answer 14

Random genetic recombination occur among multiple copies of immunoglobulin gene segments or TCR gene segments.

Question 15

Summarise the concept of clonal selection

Answer 15

• Lymphocytes that meet an antigen they recognise will proliferate and survive.
• Antigens bind to surface receptors, often in the lymph
• Selective expansion of that clone
• Effector cells fight infection

Question 16

What happens when an antigen is removed?

Answer 16

• Many lymphocytes will die after fulfilling their function

- Some remains as memory cells so the secondary response is greater and more rapid

Question 17

Compare the times taken for the innate and adaptive responses.

Answer 17

• Innate takes minutes to hours

- Adaptive takes days to weeks