ToB - Immunity

Question 0

How do epithelia respond to pathogen attack?

Answer 0

1) . They are activated upon attack.
2) . Produce cytokines (cause some cells behaviour to alter) then chemokines (attract other cells and allow leakiness) = fluid migration occurs.
3) . Opsonisation occurs (complement in blood stream)
4) . Phagocytosis
5) . Interaction of macrophage etc. with T helper cells.

Question 1

What is the function of the epithelia in immunity?

Answer 1

Form the first barrier of the innate immune system to pathogens.

Question 2

What can epithelia produce in terms of immune response?

Answer 2

1) . Cytokines - proteins that act as chemical messengers to alter the behaviour of a cell.
2) . Chemokines - proteins that attract other cells and cause them to leak.
3) . Natural antibiotics - cathelicidens, defensins
4) . MAY PRODUCE - mucins, acid

Question 3

What do inflammatory mediators do and what does this result in?

Answer 3

They promote vascular permeability
= leakage of antibodies and complement
= movement of macrophages, neutrophils and lymphocytes into tissues from blood stream.

Question 4

What are the phagocytosis performing cell components of the innate immune system and what do they do?

Answer 4

Neutrophil

• specialised for anaerobic conditions (as this prevails in damaged tissue)
• aided by receptors for bacterial constituent so can bind to bacterium and as a result phagocytose better
• contain granules of NADPH oxidase (oxidative burst) and lysozymes (phagocytosis) but once these run out, more cannot be synthesised

Monocyte/macrophage

• also act as antigen presenting cells
• aided by opsonisation
• release cytokines that activate the T lymphocytes

Question 5

What are the cellular components of the innate immune system that perform allergic reactions, and what is their function?

Answer 5

Eosinophils - antiparasite
Basophils - protect mucosal surfaces
Mast cells - protect mucosal surfaces

Question 6

What part of the immune system are natural killer cells part of, how are they activated and what is their function?

Answer 6

Part of the innate immune system.
Activated by cytokines released by macrophages (IL-12) and a chemical (IFNalpha/beta) released upon viral infection.
Induce apoptosis in a virus infected or cancerous cell.

Question 7

What is opsonisation?

Answer 7

The bacteria is coated with complement or antibodies.
Complement receptors are on phagocytes = mediate engulfment after binding.
Granules can now fuse and kill the pathogen.

Question 8

What are the humoral components of the innate immune system and their function?

Answer 8

Transferrin/lactoferrin - deprive bacteria of iron

Interferon - activate NKCs, inhibit viral replication

Lysozyme - breaks down cell wall of some gram positive bacteria

Fibronectin - opsonisation

Complement - kill microbe, aid in phagocytosis

TNF-alpha - inhibit viral replication, activates phagocytosis

Question 9

What does complement 3B do?

Answer 9

Binds to bacteria covalently and opsonises it.

Question 10

How can complement components kill a bacterium?

Answer 10

1) . C5-9 form a complex which binds to the bacteria membrane.
2) . C8 binds and inserts into membrane
3) . C9 binds to complex and causes polymerisation (forms the loop) = pore forms

= lysis of cell.

Question 11

What is the flow chart of adaptive immunity?

Answer 11

Common lymphoid precursor
= T cell = B cell
= CD4+ (helper) CD8+ (cytotoxic) = plasma cell

Question 12

What is the difference in antigen receptors of B cells and T cells?

Answer 12

In T cells, they are non membrane bound molecules (get released) = T cell antigen receptor

In B cells, they are membrane bound
= surface immunoglobulin

Question 13

What are the cellular components of the adaptive immune system and their functions?

Answer 13

B cell

• activated by CD4+ cells
• release cytokines
• divide to give plasma and memory cells

T cytotoxic cell (CD8+)
- release perforin when cell is infected (destroys cell walls)

T helper cell (CD4+)

• activated when CD4+ binds to an antigen on an antigen presenting cell
• clones to form helper cells
• activates B cells

Question 14

What do plasma cells provide?

Answer 14

Antibodies

Question 15

What are the humoral components of adaptive immunity?

Answer 15

1) . Cytokines (e.g. CD4+ activates B cells)
2) . Perforin - released by T cytotoxic cells to destroy cell walls
3) . Antibodies

Question 16

How do antibodies help with immunity?

Answer 16

1) . Neutralisation - bind to bacteria, preventing them from adhering to healthy cells
2) . Opsonisation - bind to bacteria and then are detected by receptors on macrophages = aids phagocytosis
3) . Complement activation - aids opsonisation.

Question 17

What is clonal selection in immunity?

Answer 17

Each lymphocyte has only one specific antigen = needs cloning before mounting an effective response.
This takes 3-5 days after the lymphocyte bearing the complimentary receptor to the foreign antigen is detected.

Question 18

What is the basic sequence of events in an adaptive immune response?

Answer 18

1) . Clonal selection
2) . Clonal expansion
3) . Differentiation to effector cells
4) . Antigen elimination
5) . T and B cell apoptosis

Question 19

Compare and contrast the innate and adaptive immune system.

Answer 19

Innate born with, adaptive is acquired.

Innate doesn’t have a memory, adaptive does.

Innate is non specific, adaptive has specific lymphocytes used

Innate is not enhanced by a second exposure, adaptive reacts much quicker due to presence of memory cells.

Question 20

How can complement be destroyed or deficient?

Answer 20

By heat

By genetic defect causing a deficiency in a specific complement.