Immune System

Question 1

How do pathogens gain entry to the host?

Answer 1

• Enter through external contact

- Through mucosal surfaces (airways, GI tract, reproductive tract)

Question 2

Where does the innate immune response occur?

Answer 2

Occurs locally to the site of infection

Question 3

How are neutrophils involved in the innate response?

Answer 3

They kill pathogens which enter by phagotysing them and then releasing granules(which contain bacteriostatic and toxic factors) inside the cell which kills the pathogen. They then kill themselves.

Question 4

How are macrophages involved in innate response?

Answer 4

Engulf bacteria and inside the cell fuses with granules (from lysosome) which releases toxic contents to kill bacteria. Also plays a role in removal of waste.

Question 5

What are complements?

Answer 5

Collections of plasma proteins and molecules which all work together to complement the killing in our immune system.

Question 6

What pathways activate complements?

Answer 6

• Classical pathway
• Alternative pathway
• MB-Lectin pathway

Question 7

What does activation of complements caused?

Answer 7

• Recruitment of inflammatory cells
• Opsonization of pathogens (coating of bacterial surfaces to make it nicer for phagocytes)
• Killing of pathogens

Question 8

How do cells involved in innate response migrate to site of infection?

Answer 8

• Rolling adhesion; cells roll around in blood
• Tight binding; no. of receptors and counter ligands on cell cause physical interaction which make it stick to blood vessel wall
• Diapedesis; when it gets right signal it begins to make its way through the very tight wall of the blood vessel
• Migration; they then migrate to the site of infection and are attracted to signals to get there (chemotactic factors).

Question 9

What factors are released in their response and what is their function?

Answer 9

-Cytokine
-Chemokine
They cause increased vascular permeability and release chemotactic factors which allow neutrophils to migrate out and phagocytose.

Question 10

What are the primary lymphoid organs?

Answer 10

• Bone marrow

- Thymus

Question 11

What are the secondary lymphoid organs?

Answer 11

• Lymph nodes

- Spleen

Question 12

Where are b-lymphocytes produced and mature?

Answer 12

Produced in bone marrow, with further maturation in the spleen/ lymph node.

Question 13

Where are t-lymphocytes produced and mature?

Answer 13

Precursors from bone marrow and mature in the thymus.

Question 14

What is the role of the spleen?

Answer 14

• filters the blood

- collects blood borne antigens and fliters them

Question 15

What is the role of the thymus?

Answer 15

• Selection of auto reactive cells for removal to prevent autoimmunity
• Export of repetoire of T cells for life
• Area of maturation of t lymphocytes

Question 16

What is the structure on antibodies?

Answer 16

-Y shaped, sticky, specific and binds to cells.

Question 17

What is the function of antibodies?

Answer 17

-They neutralise and eliminate microbes

Question 18

How do antibodies function?

Answer 18

• They act by neutralising bacteria, the arms connect to bacteria and tail connects to macrophage
• Opsonization can also occur as they coat bacteria, enhancing phagocytes
• Antibodies can also activate compliments

Question 19

Where does the adaptive immune response occurs?

Answer 19

Occurs in specialised places called lymphoid organs

Question 20

What cells are involved in the adaptive response and what are their features?

Answer 20

• Driven by B and T-lymphocytes
• They are small and motile and dont phagocytose.
• They proliferate and make daughter cells

Question 21

How can we classify t lymphocytes?

Answer 21

Once they leave the thymus they will become:
-CD4+ (helper) OR
-CD8+ (killer)
CD4+ will all stay helper cells but will divide further into different types.

Question 22

What are MHC antigens?

Answer 22

Are molecules on the surface of the antigen presenting cell that will present antigens to t-cells.

Question 23

What are the different types of MHC and their differences?

Answer 23

• Class 1 ; is on all nucleated cells and presents to CD8+ cells.
• Class 2; presents to CD4+ cells.

Question 24

How do t-cells kill?

Answer 24

They do this by inducing apoptosis, it does so by putting perforin in the cell membrane and then injects granzymes which will induce apoptosis.

Question 25

How do helper t cells help?

Answer 25

Produce factors that activate virtually all the other immune system cells. Including B lymphocytes.

Question 26

How do t lymphocytes recognise antigens?

Answer 26

They react with antigen presenting cells, activating t cells as the t cell receptor will recognise the antigen presented to it.

Question 27

How do B-lymphocytes work?

Answer 27

They become plasma cells at last stage of maturation, become like a factory for producing antibodies.
Mature B cells have membrane bound antibodies on their surface.