Immunoglobulins

Question 1

Which amino acids are most common in the hinge regions of Igs? What are their functions?

Answer 1

• Cysteine: present for disulfide bonds between the heavy chains
• Proline: present to provide flexibility to the two antigen binding arms

Question 2

Which Ig’s do not have hinge regions?

Answer 2

IgM and IgE. They have an extra domain instead. Their CH2 domain preforms a hinge-like function

Question 3

Cleavage of Ig’s with Papain

Answer 3

• PApain cleaves the Ig’s Above the disulfide bond of the hinge region
• Forms 3 Ig fragments: two Fab fragments which bind the antigens and one Fc fragment which binds to the cells

Question 4

Cleavage of Ig’s with Pepsin

Answer 4

• Pepsin cleaves the Ig’s below the disulfide bond of the hinge region
• Forms two main fragments: one F(ab’)2 fragment which contains both of the antigen binding arms and a partial Fc fragment

Question 5

CD79

Answer 5

The signal transduction component of the B cell receptor. It is a heterodimer made up of Ig-alpha and Ig-beta components

Question 6

Two functions of Ig’s

Answer 6

1. Effector Functions: how the Igs interact with other components of the immune system
2. Antigen recognititon

Question 7

Which chromosomes are the Kappa LC, Lambda LC, and HC located on?

Answer 7

Kappa LC: 2
Lambda LC: 22
HC: 14

Question 8

What are two conditions that arise from mutations in RAG genes?

Answer 8

1. Severe Combined Immunideficieny (SCID)
2. Omenn’s syndrome
   - These patients cannot synthesize antibodies