Introduction

Question 1

What is the immune system?

Answer 1

Molecules, cells and tissues that mediate immune responses

Lymphatic system, blood, interaction of immune organs

Question 2

What tissues are associated with the immune system?

Answer 2

Lymph node, lymphatics, spleen, bone marrow, thymus

Question 3

What molecules are associated with the immune system?

Answer 3

Complement- system of soluble serum proteins
Cytokines- immune messenger hormones (chemokines- specialise in making cells move)
Antibodies- secreted molecules bind to pathogens (adaptive)

Question 4

What cells types are associated with the immune system?

Answer 4

Leukocytes- all immune cells/ white blood cells
Innate- macrophages, dendritic, neutrophils, eosinophils, basophils, mast
Adaptive- T cells, B cells, lymphocytes

Question 5

Where are immune cells made?

Answer 5

Bone marrow and thymus

Question 6

Where do adaptive immune cells spend most of their time?

Answer 6

Lymph nodes and spleen

Question 7

What is the purpose of lymphatics?

Answer 7

Drainage for periphery/ scanning for danger
Lymph nodes at lymphatic junctions
Drain into subclavian veins/ blood via thoracic duct

Question 8

What are lymph nodes?

Answer 8

Highly organised accumulations of immune cells at lymphatic junctions
Swell during infection- lymphadenopathy

Question 9

What is the difference between primary and secondary lymphoid organs?

Answer 9

Primary- immune cells are made, bone marrow- T cells mature in thymus (exported precursor)
Secondary- where immune responses are initiated, lymph nodes and spleen, tonsils appendix and Peyer’s patches in the gut

Question 10

List barriers to prevent entry of extracellular pathogens

Answer 10

Physical- skin (dead so virus cannot replicate), gut epithelium (rapid turnover)
Chemical- low pH of skin, vagina and stomach
Flushing- tears, sweat, mucus
Antimicrobial peptides- small proteins directly toxic to bacteria, present in many secretions
Competitive- commensal bacteria out compete dangerous bacteria

Question 11

What do virally-infected cells release?

Answer 11

IFN alpha and beta

Induces antiviral state in neighbouring cells

Question 12

What happens in an anti-viral state?

Answer 12

Upregulate antiviral proteins (IFNs) and antigen presentation
Downregulate everything else by degrading mRNA and inhibiting protein translation factors (suppress viral proliferation)

Question 13

How can an antiviral state be mimicked in a clinical setting?

Answer 13

Synthetic IFN a administration is highly effective in Hepatitis B virus infection

Question 14

What are the pros of an immune system?

Answer 14

Protect against infection, immunity to reinfection/ vaccination response, kills mutated tumour cells, higher risk of cancer after transplants due to immunosuppression

Question 15

What are the cons of an immune system?

Answer 15

Energy intensive, wasteful, causes disease- allergy (hay fever, asthma, eczema), autoimmunity (MS, Rheumatoid arthritis, Lupus), inflammatory bowel diseases
Mediates transplant rejection

Question 16

What are pathogens?

Answer 16

Bacteria/ virus/ fungus/ protozoa/ helminth parasites
Intracellular and extracellular
Diversity in size and type

Question 17

What is danger?

Answer 17

Signals indicating there is harm to the body, and/or infectious agents and present, recognised by innate immune response

Question 18

How does the immune system distinguish between self and non-self?

Answer 18

Recognise own proteins- no attack
Kill non recognisable cells
Recognised by adaptive immune response

Question 19

What are the types of danger signals?

Answer 19

PAMPs- Pathogen Associated Molecular Patterns
- types of molecules only produced by infectious against and not host tissue
- Bacterial cell wall constituents (LPS)
DAMPs- Damage Associated Molecular Patterns
- Molecules released from injured cells
- DNA, RNA, ATP, breakdown products of extracellular matrix

Question 20

What is the difference between apoptosis and necrosis?

Answer 20

Apoptosis- programmed cell death, caspases activated, fragmentation of DNA, blebbing of membrane, phagocytosis, non-inflammatory
Necrosis- uncontrolled cell death, cell ruptures, contents release, highly inflammatory (DAMPs), mechanical damage from pathogen bursting out

Question 21

What are PRRs?

Answer 21

Pattern Recognition Receptors for PAMPs and DAMPs
Toll-like Receptors
TLR3- binds double stranded RNA in viruses
TLR4- bind LPS
TLR5- binds flagellin (flagellated bacteria)

Question 22

How is negative selection used in the immune system?

Answer 22

Different T and B cells, develop randomly (wasteful)
Kills those that react to self antigens
Mature adaptive immune cells

Question 23

What is the difference between adaptive and innate immune responses?

Answer 23

Innate- detects danger, rapid and generic response, communicates danger to adaptive
Adaptive- differentiates between self and non-self, slow and highly specific response, memory to antigens it has seen before

Question 24

What are the different strengths of immune response?

Answer 24

Susceptibility, Immunity, Immunopathology
Old/ young general susceptible
Cytokine storm- overactive immune response can kill

Question 25

What happens when the immune responds to something it shouldn’t?

Answer 25

• Harmless environmental molecules (allergy) o self (autoimmunity)
• Fatal anaphylactic shock/ hard to treat