Antibody Effector Functions

Question 1

List antibody effector functions

Answer 1

1. Neutralization (Fab)
2. Opsonization (Fc)
3. ADCC (Fc)
4. Sensitization of mast cells (Fc)
5. Activation of complement (Fc)

Question 2

How does neutralization occur?

Answer 2

By binding to pathogens; viruses, bacteria or toxins so they’re unable to cause cellular damage
Occurs in fluids

Question 3

What is opsonization?

Answer 3

Process by which a pathogen is marked for destruction by ADCC, ADCP or complement system.
Phagocytes (neutrophils, macrophages) have FcRs for IgG and when one binds to Fc portion of Ab covering the pathogen, uptake is enhanced
Modification of Ag by opsonins, making them more susceptible to phagocytes
NK cell can kill target cell which then dies by apoptosis

Question 4

What is ADCC?

Answer 4

= antibody dependent cell-mediated cytotoxicity (AKA NK cell sensitization)
Helminth, eosinophils secrete toxins to damage wormq

Question 5

How are mast cells activated?

Answer 5

IgE activation

Ag binds to the FcR on the mast cells and basophils, which leads to allergy symptoms

Question 6

How is the complement system activated via the classical pathway?

Answer 6

IgM, IgA and some IgG can activate the cascade by 1) Ab Fab binds to pathogen
2) Clq complement component binds to Fc regions of bound antibodies, which causes complement activation