Week 5- Immune Tolerance

Question 1

What is immune regulation?

Answer 1

Control of the immune system to prevent inappropriate responses against pathogens or self cells

Question 2

What does immune regulation help avoid?

Answer 2

Tissue damage, excessive lymphocyte activation

Question 3

What arises if there is failure in immune regulation?

Answer 3

Inflammatory disease

Question 4

What are the 3 main problems that arise due to failure of immune regulation?

Answer 4

Autoimmunity, allergy, hypercytokinemia/sepsis

Question 5

What is autoimmunity and how can it arise?

Answer 5

Immune response against a self antigen, can be systemic or organ specific, occurs due to genetic susceptibility or environmental triggers

Question 6

What is allergy?

Answer 6

Immune response against a non infectious agent that can cause tissue damage or disease

Question 7

What are the 2 ways allergies are mediated? Give an example for each

Answer 7

1. Antibodies and mast cells: acute anaphylactic shock

2. T cells: delayed type hypersensitivity

Question 8

What is hypercytokinemia?

Answer 8

A very excessive immune response eg fever

Question 9

What is sepsis?

Answer 9

Pathogens entering the wrong body compartment

NOTE sepsis is not just blood infection, this is known as septicaemia

Question 10

What are the 3 stages required to cause an immune response?

Answer 10

1. Antigen recognition
2. Co stimulation
3. Cytokine production

Question 11

What is an immune synapse?

Answer 11

An area cleared to allow many T cells to come together and communicate

Question 12

What are the 3 phases of cell mediated immunity?

Answer 12

1. Induction: foreign antigen recognized, components displayed on MHC and T cell involvement starts
2. Effector: T cell is activated and proliferates
3. Memory: Pool of T cells is reduced to some are kept as memory

Question 13

What are the 3 outcomes of an immune response?

Answer 13

1. Resolution: everything returns to normal with no tissue damage
2. Repair: healing with scar tissue formation (fibroblasts and collagen synthesized)
3. Chronic inflammation: ongoing persistent attempts to repair damage

Question 14

What is central tolerance? How do B and T cells undergo it?

Answer 14

When self B/T cells are destroyed before they enter circulation.

For B cells, if in the bone marrow they encounter an antigen that can cross link their IgM they undergo apoptosis

For T cells if it doesn’t bind to MHC or binds to self MHC strongly, they undergo apoptosis

Question 15

What is peripheral tolerance?

Answer 15

When self B/T cells are destroyed in circulation

Question 16

What is AIRE?

Answer 16

A specialized transcription factor that allows thymic expression of proteins from the whole genome so that T cells can see many diff proteins

Question 17

What are the 3 states T cells can be in?

Answer 17

1. Anergy: T cells need co stimulation to be activated but when they see MHC with without co stimulatory protein they enter a state of anergy/shut down
2. Ignorance: there may be costimulation but not enough to induce a T cell response
3. Antigen induced cell death: when there is no co stimulation and the T cell is killed

Question 18

What are the subtypes of T helper (CD4) cells?

Answer 18

Th1/2/17, Tfh, Treg

Question 19

What does Th1 do?

Answer 19

It produces interferon gamma which boosts intracellular responses

Question 20

What does Th2 do?

Answer 20

Produces IL 3/4/5 which boosts the multicellular response

Question 21

What does Tfh do?

Answer 21

Follicular helper, it produces IL 21 which allows generation of isotope switched antibodies

Question 22

What does Th17 do?

Answer 22

Helps fight bacteria by producing IL17

Question 23

What does Treg do?

Answer 23

Controls the immune response, inhibits other T cells, helps produce IL10 which shuts down the immune response

Question 24

What is cross regulation?

Answer 24

The phenomenon wherein if one type of T cell is produced, it inhibits other types of T cell to refine the immune response and increase effectiveness

Question 25

How does IL10 work?

Answer 25

It blocks pro inflammatory synthesis