Antibodies

Question 1

What is the name of a site on an antigen recognized by an antibody or an antigen receptor?

Answer 1

Epitope

Question 2

What is affinity?

Answer 2

Binding of one Fab (variable region) region with one epitope

- Multiple identical epitopes within a single antigen provide multiple binding sites, producing high affinity binding

Question 3

Whis is avidity?

Answer 3

Overall attraction/binding between the two molecules

Question 4

How do avidity and affinity affect immunity?

Answer 4

If the affinity and avidity are high, the likelihood that the antibody will provide protective immunity is high

Question 5

What are the functions of the constant and variable regions?

Answer 5

• Constant region of heavy chain alter effector function. Interacts with host.
• Variable region of heavy chain remains the same (specificity). Dictates interaction with the pathogen.

Question 6

Which of the Fc and Fab can change and which stays the same?

Answer 6

The Fc (constant) region can change
The Fab (variable) region stays the same

Question 7

Which Ig has the highest conc in a serum antibody titre when there is a second antigen challenge?

Answer 7

IgG

Question 8

What are the characteristics of a primary response?

Answer 8

• Short lived
• Low magnitude
• Isotype is IgM
• Initiated by local lymph nodes
• Memory cells established

Question 9

What are the secondary response characteristics?

Answer 9

• More rapid
• Longer duration
• Higher magnitude
• Initiated by local lymph tissues
• Isotype switches to predominance of IgG & IgA
• Higher affinity for antigen

Question 10

How is the antibody synthesised?

Answer 10

By blasting B lymphocytes and plasma cells

Question 11

Describe what occurs following an antigen binding to a B-cell receptor

Answer 11

• B-cells divide and replicate
• Some B-cells become memory cells
• Most B-cells become plasma cells which release antibodies

Question 12

What are the functions of antibodies?

Answer 12

• Neutralise by binding to prevent pathogen attachment, invasion of host cells, replication and toxin production
• Activate complement system
• Phagocytosis/Opsinisation by Fc receptors and complement receptors

Question 13

What is the function of IgA?

Answer 13

• A tissue specific effector
• Secreted locally to mucosal tissues by B-cells
• Passes into lumen
• Receptor is proteolysed to leave secretory component attached to protect IgA on mucosal surfaces