Antibodies

Question 1

Antibody Structure

Answer 1

1) 4 polypeptide chains
2) Chains
- Heavy Chains
- Variable regions (Fab)
- Constant regions (Fc)
- Light Chains
- Variable regions (Fab)
- Constant regions (Fc)

Question 2

Determinant types

Answer 2

1) Allotypic
- Allelic differences - we all have IgG with subtle differences

2) Idiotypic
- Antigenic determinants on the V regions (area where Ag binds)

Question 3

Classes of Antibodies

Answer 3

1) IgM
2) IgG
3) IgA
4) IgE
5) IgD

Question 4

IgM

Answer 4

• 5-10% of serum Abs
• Produced in PRIMARY RESPONSE to antigen
• 10 antigen binding sites
• Good at binding to viruses, RBCs
• Generally low affinity

Question 5

IgG

Answer 5

• Main secondary immune response Ab (MOST PROTECTIVE Ab)
• 80% of total serum Abs
• Subclasses (IgG1, IgG2, IgG3, IgG4)
• Classical Complement Pathway “Fixer”
• Only Ab that can cross placental barrier

Question 6

IgA (serum and secretory)

Answer 6

• Important in Secondary immune response
• 10-15% in total serum
• Secretory IgA
  - Predominant in mucosa, saliva, tears, etc.
  - Produced by epithelial cells
  - Important because they are at entry point for antigens
  - Comes to fetuses through breast milk

A = Ass which means intestines and secretory :)

Question 7

IgE

Answer 7

• Part of secondary immune response
• Key Traits:
  1) Low serum concentration
  2) Binds to basophils and tissue mast cells (high affinity)
  3) Protects against Parasites!!! (Helminthes)

Question 8

IgD

Answer 8

• Present on Mature B cells

- mIgM may also be present on same B cell but both will have same antigen specificity

Question 9

How are immunoglobulins bifunctional?

Answer 9

1) They bind to Ags and promote killing

2) They bind to Ags to initiate the classical component pathway

Question 10

How do Abs bind to Ags?

Answer 10

Non-covalent bonding but high-affinity interaction

Question 11

What is Affinity?

Answer 11

How strong the interaction is between the univalent Abs and the univalent Ag?

Question 12

What is avidity?

Answer 12

Strength between a multivalent Ab and multivalent Ag

Question 13

What happens to antibodies following B cell activation?

Answer 13

They have a much higher affinity for an antigen and will switch antibody class (isotope switching)

Question 14

What are monoclonal antibodies?

Answer 14

• mAb

- Abs that are all identical produced by one cell -> Immune cells that are all clones of one parent cell