Immunology 6

Question 1

Define immune memory.

Answer 1

Immune memory = the ability of the immune system to remember antigens from pathogens and mount an immune response of greater magnitude and with faster kinetics upon re-encounter of same antigens.

Question 2

What are the key features of effective vaccines?

Answer 2

Safe
Protective
Induces neutralising antibody
Induces protective T cells
Practical considerations - low cost per dose / biological stability / ease of admin / few side effects

Question 3

What are the 5 types of vaccines?

Answer 3

Live attenuated
Inactivated/killed
Toxoid (modified toxin)
Subunit (conjugate)
Adjuvant

Question 4

Define immune tolerance.

Answer 4

Immune tolerance = processes which prevent the immune system from attacking healthy self cells.

Question 5

Describe central tolerance.

Answer 5

Occurs during T cell development in the thymus.

T cells which have receptors specific for self-antigens are identified and deleted.

Some weakly self-reactive cells may escape and are controlled by peripheral tolerance.

Question 6

Describe peripheral tolerance.

Answer 6

Immune tolerance that occurs in peripheral body tissues (outside thymus).

Occurs during T cell’s lifetime, not during development.

Involves lack of signal 2 and 3 during T cell activation, and regulatory T cells (T regs).

Question 7

What role does the lack of signal 2 and 3 during T cell activation play in peripheral tolerance?

Answer 7

Weakly self-reactive T cell will not activate unless it has strong signal 2 and 3 from DCs.

DCs do not provide this unless they detect danger in the form of PAMPs and DAMPs.

Therefore weakly self-reactive T cells only activate in presence of pathogens if T cells abort their activation - called anergy.

Question 8

What role do T regs play in peripheral tolerance?

Answer 8

T regs made in thymus or arrive when CD4+ Th0 cells differentiate into T regs and produce cytokines (IL-10, TGF-beta) to switch off immune responses.

T regs can also turn off weakly self-reactive T cells if they activate accidentally.

Question 9

Define autoimmunity.

Answer 9

Autoimmunity = clinical syndrome characterised by a break in immune tolerance, permitting immune responses directed at self tissues.

Question 10

Define hypersensitivity reactions.

Answer 10

Hypersensitivity reactions = a group of excessive immune responses to (usually harmless) molecules.

Question 11

What are the 4 types of hypersensitivity?

Answer 11

Type I = immediate (allergy)

Type II = antibody-mediated

Type III = antigen-antibody complex

Type IV = delayed