Antibody function

Question 1

Which pathway of complement may be activated by antibody binding to antigen? What is the end result of the activation of this pathway?

Answer 1

Classical pathway (Antibody mediated)
- leads to cell lysis (via formation of membrane attack complex = MAC)

Question 2

In ADCC, which immune cell is activated, which isotype of immunoglobulin is involved and which cells are targeted by this immune response? What’s the end result

Answer 2

NK cells recognise Fc portion of IgG on tumour cells & virally infected cells
=> NK degranulate to kill target cell

Question 3

Only one class of immmunoglobulin is transferred placentally. Which one, and what biological purpose does this passive transfer have?

Answer 3

IgG passed from mother to foetus for passive immunity prior to birth

Question 4

Explain how antibody molecules can neutralise bacterial toxins/venom? and which antibody isotope is involved?

Answer 4

IgG bind to toxins/venom to it from interacting w/ host cell

Question 5

Which Ig can bind to viral particles? How does this attachment inhibit viral infection?

Answer 5

IgG, IgA, IgM antibodies bind & coat surface of virus particle ≠ attach & penetrate in host cell

Question 6

Describe the process of antibody opsonisation. Which isotype of immunoglobulin is involved?

Answer 6

IgG bind to epitope on antigen molecule of pathogen = coat pathogen = phagocitised by PMN, & macrophages

Question 7

Why is IgM the isotype of immunoglobulin that has the best agglutinating ability? Why is IgA next best?

Answer 7

1. IgM has the best agglutinating ability because it has 5 Ab bound together like a star = 10 antigen binding sites
2. IgA is next best bc can be a dimer (2 Ab tog.) = 4 abs

Question 8

Briefly describe the Ab produced during the primary and secondary exposure of the immune system to an antigen?

Answer 8

1º: IgM produced 1st -> IgG [ ] slightly above IgM

2º: IgM produced 1st & less [ ] as 1º -> IgG rapidly produced & @ higher [ ] than 1º

Question 9

Why can the release of histamine cause asthma in susceptible people? i.e. what biological effect does it have?

Answer 9

histamin => vasodilate = BV leaky = edema (swelling) = mucous secretion & smooth muscle in bronchioles contract

Question 10

what’s ADCC?

Answer 10

Antibody Dependent cell-mediated cytotoxicity.

Question 11

Briefly describe the events that occur during the primary and secondary exposure of the immune system to an antigen?

Answer 11

1º: antigen binds to IgD on B-cell (act as receptor) = B cell activated => a) memory B cell or plasma cell (produce Ab)
2º: B cell converting to a plasma cell changes its Ig to IgM or IgA, G, E (assisted by helper T cells)

Question 12

primary function of antibodies

Answer 12

stick to target molecules via epitopes on antigens

Question 13

Function of IgE and which cell is activated

Answer 13

defence against parasites and involved in allergic reactions. Eosinophil activated

Question 14

Briefly describe the events that occur during the primary and secondary exposure of the immune system to an ALLERGEN?

Answer 14

1º: IgE (made by B cells) bound to basophils/mast cells

2º: degranulation/release of hsitamine