4 - Antibodies

Question 1

define an antibody

Answer 1

a protein that is produced in response to a fogey molecule (an antibody), and has the property of binding specifically to that antigen

Question 2

When an antigen binds, what happens to the Fc part of the immunoglobulin?

Answer 2

changed conformation and can perform effector function such as activating complements

Question 3

Around how many interactions are there between an antigen and an antibody?

Answer 3

20

Question 4

Where are the hyper variable regions and what do they do?

Answer 4

located at loops at the ends of proteins/V domains

they are the areas that interact with the antigen

Question 5

Why is avidity a better measure of binding capacity than affinity?

Answer 5

• affinity is between a single antigen and antibody binding site
• but antibodies have a minimum of 2 binding sites
• avidity considers multiple interactions between an antibody with multiple binding sites and antigens with multiple epitopes

Question 6

How do different classes of antibodies differ?

Answer 6

in their constant regions of their heavy chains

Question 7

Ig G

Answer 7

• 4 subclasses that differ mainly in the hinge region and effector function domains
• passes across the placenta
• major activator of complements (classical pathways)

Question 8

Ig A

Answer 8

• monomer in blood, dimer when secreted
• protects mucosal surfaces
  DIMER FORM (secretory)
• joined by J chain
• has a secretary component, that helps to protect the molecule from being degraded by the enzymes found on the mucosal surfaces

Question 9

In secretory IgA, how are the immunoglobulins joined together?

Answer 9

J chain

Question 10

Where does the secretory component of secretory IgA come from?

Answer 10

derived form the poly-Ig receptor

Question 11

IgM

Answer 11

• pentameric
• all joined by a J chain and held together by disulphide bonds
• mainly confined to the blood
• first Ig produced after exposure to antigen
• low affinity, high avidity- activates complement

Question 12

IgD

Answer 12

• low serum concentrations

- involved in B cell development and activation

Question 13

IgE

Answer 13

• produced in response to parasitic infection and allergic disease
• binds to high affinity Fc receptors of mast cells and basophils
• triggers mast cell activation and histamine release

Question 14

What is the first immunoglobulin type to be produced after exposure to antigen?

Answer 14

IgM

Question 15

Antibodies are which type of immunoglobulin?

Answer 15

gamma (IgG)

Question 16

Which is the main immunoglobulin in the extracellular fluid?

Answer 16

IgG

Question 17

Which immunoglobulin is secretory?

Answer 17

Dimeric IgA