5. Immunoglobulin Classes- Structure and Function Part II

Question 1

How many subunits are there in an IgM molecule and how are they held together?

Answer 1

• 5 subunits

- held together by sulfide bonds

Question 2

Why is IgM more efficient at agglutination and complement fixation than IgG?

Answer 2

IgM has a higher valencey due to the fact that there are 10 antigen binding site. Therefore, one molecule of IgM can bind to 5 or more Ag (depending on size/steric hindrance), while IgG can only attached to up to 2 Ags.

Question 3

Which Ig class is the first to be produced in an immune response? Which is the first to be produced during development of the infant?

Answer 3

IgM is the first for both cases

Question 4

Which immunoglobulin is found in breast milk?

Answer 4

IgA

Question 5

What is the function of the secretory component found in the IgA molecule?

Answer 5

• facilitates transport into secretions

- protects Ig from degradation

Question 6

What types of cells are involved in allergic reactions mediated by IgE? in parasitic infections?

Answer 6

Allergic Reactions

• Basophil (blood)
• mast cell (tissue)

Parasitic infections

• neutrophils
• eosinophils

Question 7

Which type(s) of antigenic determinants are found in the variable regions of an Ig? in constant regions?

Answer 7

Variable region
-idiotypes

Constant region

• Isotypes
• Allotypes

Question 8

Isotypes are present in all members of a species, but how do they vary?

Answer 8

• differ between species

- differ between Ig classes and subclasses