Chapter 15: Adaptive Immune Response - Antigen and Antibody Structure Flashcards
-What is an antigen? (2)
- antibody generator
- any molecule that induces antibody production or binds to a specific receptor on a B or T cell
Which part of the antigen does an antibody recognize?
- small part of the antigen called an epitope
A foreign particle, like bacteria, will have what antigens and epitopes?
- several antigens
- a vast array of potential epitopes
Some antigens are more immunogenic than others. What does this mean?
- they elicit a stronger immune response
NOTE that the most common antigens are proteins
What are antibodies (immunoglobulins)?
- Y-shaped proteins that bind to antigens in a very specific manner
What are some properties of antibodies? (3)
- like a lock and key
- only an antigen with the correct epitope will be bound
- each antibody binds to ONLY ONE antigen
What does each antibody consist of? (5)
- four polypeptides:
- 2 light chains
- 2 dark chains
- 2 identical arms (Fab region)
- one stem (Fc region)
What is the Fab region? (3)
- 2 identical arms
- variable fragment
- each has an identical antigen binding site specific for one epitope
What is the Fc region? (3)
- constant fragment
- binds to complement proteins, phagocytes, etc.
- allows the antibody to trigger other components of immunity
What are the 6 protective functions of antibodies?
- cross linking
- neutralization
- complement activation
- Opsonization
- Ab dependent cytotoxicity
- immobilization and prevention of adherence
What occurs in cross-linking?
- antigens get stuck together
- reduces number of infectious units to be dealt with
What occurs in neutralization? (2)
- Ab (antibody) binds to and inactivates toxins, bacteria, viruses
- Blocks attachment sites
What occurs in complement activation? (2)
- Ab binds bacteria, which acts as a starting point for complement pathway
- MAC attack
In lecture, which protein is positioned in phospholipid bilayer in GRAM - cells?
C5B
What occurs in opsonization?
- Ab flags down phagocytic cells to engulf and destroy the antigen
What occurs in Ab dependent cytotoxicity?
- Ab flags down immune system cells to destroy abnormal or infected body cells
What occurs in immobilization and prevention of adherence? (2)
- Ab binds to flagella to stop antigen from moving
- Binds to pili to stop bacteria from colonizing (GRAM -)
