C4.

Question 1

complement

Answer 1

cell lysis/ C1q –> membrane attack complex

Complement proteins on bacterium are recognised by complement receptors on phagocytes

Question 2

neutralisation

Answer 2

antibodies bind and block the toxin, stop it from binding to receptor

Question 3

opsonisation

Answer 3

antibodies bind bacterial membrane, mark as foreign for phagocytes by binding of Fc to Fc receptor

Question 4

thymus dependent antigen

Answer 4

BCR, (Tfh)TCR: MHC-II + CD40-CD40L

Question 5

thymus independent antigen

Answer 5

BCR (polyvalent antigen) LPS/TLR

Question 6

steps of antibody mediating killing in NK cells

Answer 6

1. Antibody binds antigens on surface target cell
2. Fc receptors on NK cell recognise bound antibody
3. Crosslinking of Fc receptors signals the NK cell to kill
   the target cell
4. target dies via apoptosis

Question 7

How does antibody mediate in damage

/killing by granulocytes

Answer 7

1. resting mast cells have granules containing histamine/ other inflammatory mediators
2. multivalent antigen crosslinks bound IgE antibody, causing release of granule contents

Question 8

Which antibody in important in protecting the gut

Answer 8

Dimeric IgA -binds to layer of mucus overlying gut epithelium
IgA neutralizes pathogens & their toxins