Classes of Antibodies

Question 1

What are the 5 classes of immunoglobulins?

Answer 1

IgM, IgG, IgA, IgE and IgD

Question 2

What is the structure of IgM? How is this structure useful?

Answer 2

Pentamer - Large number of antigen bindings sites

Question 3

When is IgM released?

Answer 3

First molecule released after pathogen encounter (release in 1ary response, disappears after 10 days, limited release in 2ary response)

Question 4

What are the main functions of IgM?

Answer 4

1. Kills bacteria (binding induces Fc region to activate complement pathway)
2. Activates macrophages to phagocytose pathogens
3. Serves as B cell receptor

Question 5

When is IgG released?

Answer 5

Main antibody of secondary response and late in primary response

Question 6

What is structure of IgG?

Answer 6

Monomer

Question 7

How abundant is IgG?

Answer 7

Most abundant antibody in blood

Question 8

How does IgG assist in foetus protection?

Answer 8

Is only antibody that can pass through placenta, providing immunological protection for foetus

Also secreted into mother’s milk

Question 9

What are main functions of IgG?

Answer 9

1. Activate complement cascade
2. Trigger macrophages (Fc region binds to macrophages)
3. Neutralises toxins
4. Opsonisation

Question 10

Where does IgG enter?

Answer 10

Tissue space

Question 11

What is main function of IgE monomer?

Answer 11

Antibody of allergy and antiparasitic activity

Question 12

How is IgE involved in allergic reactions?

Answer 12

Stimulates mast cells to release histamine as Fc region binds to mast cells

Question 13

How is histamine involved in allergic reactions?

Answer 13

Causes dilation and increased permeability of blood vessels leading to symptoms

Question 14

What is main function of IgD monomers?

Answer 14

Immature B cell receptors - found in B cell membrane

Question 15

What is main function of IgA secretory dimer?

Answer 15

Main component of mucus, tears, saliva to protect entrance of pathogens