4.1.7: Antibodies Flashcards
1
Q
What are antigens?
A
- Molecules that can stimulate an immune response (production of antibodies)
- Usually proteins or glycoproteins in the plasma membrane of a pathogen.
2
Q
Why do our own antigens not stimulate an immune response?
A
They are recognised by our immune system.
3
Q
What are antibodies?
A
- Immunoglobins.
- Complex proteins produced by the plasma cells in the immune system.
4
Q
How do antibodies work?
A
- They have a region with a specific shape that is complementary to that of a particular antigen.
- our immune systems must manufacture one type of antibody for every antigen that is detected.
- Antibodies attach o antigens and render them harmless.
5
Q
What is the structure of an antibody?
A
- Y-shaped with two distinct regions (2 light, 2 heavy)
- Consist of four polypeptide chains.
- Variable region (shape specific to antigen)
- Constant region (site for easy binding of phagocytic cells)
- Hinge-region (allows flexibility so molecule can grip more than one antigen)
- Disulfide bridges (hold polypeptide chains together)
6
Q
What are the three main groups of antibodies?
A
- Opsonins
- Agglutinins
- Anti-toxins
7
Q
How do opsonins work?
A
- Antibodies that bind to antigens on pathogen.
- They then act as binding sites for phagocytic cells.
- Phagocytic cells can bind to and destroy the pathogen.
8
Q
How are some opsonins not very specific?
A
- They stick to types of molecules not found in the host cell.
- e.g. peptidoglycans found in cell walls of bacteria.
9
Q
How are some opsonins specific?
A
- Produced as part of the immune response.
- Bind to very specific antigens.
10
Q
How can opsonins neutralise pathogens?
A
- Antigen on a pathogen used for attachment to host cell.
- Opsonin binds to antigen, rendering the antigen useless.
- This process is known as neutralisation.
11
Q
How do agglutinins work?
A
- Each antibody molecule has two binding sites.
- It is able to ‘crosslink’ pathogens by using each binding site to bind a different pathogen.
- When many antibodies perform this crosslinking, they clump together (agglutinate) pathogens.
12
Q
What is the benefit of agglutinating pathogens?
A
- Agglutinated pathogens are physically impeded from carrying out some functions, such s entering host cells.
- Agglutinated pathogens are easily engulfed by phagocytes.
13
Q
How do antitoxins work?
A
- Antibodies bind to molecules that are released by pathogenic cells.
- These molecules may be toxic and the action of the antitoxin renders them harmless.
14
Q
What is the primary immune response?
A
- Infecting agent detected, immune system starts to produce antibodies.
- Takes a few days before the number of antibodies in the blood rises to a level that can combat the infection.
- Once the pathogens have been dealt with, the number of antibodies in the blood drops rapidly.
15
Q
Describe the secondary immune response.
A
- B memory cells and T memory cells circulating in the blood.
- These cells recognise the specific antigens and the immune system can act quicker.
- This time, production of antibodies starts sooner and more rapidly.
- Conc. antibodies rises sooner and reaches higher concentrations.
- Quick enough to prevent symptoms being detected by the host.
