the structure and function of antibodies Flashcards
What is an antibody?
An immunoglobulin (Ig) that is a glycoprotein capable of recognising and specifically binding to an antigen (Ag)
Vital role in the immune response. Antibody (Ab) and immunoglobulin (Ig) are the same thing.
Where are antibodies found?
Can be free or membrane bound
* In serum
* In secretions (mucous, milk, saliva, tears)
* On the surface of B lymphocytes
Forms part of the B cell receptor.
What is the role of antibodies in the immune response?
Neutralises foreign molecules and binds specifically to antigens
The function of an antibody depends on its shape.
What are the two types of light chains in antibodies?
Kappa and lambda
There are five types of heavy chains: gamma, alpha, delta, mu, and epsilon.
What is the significance of the variable region in antibodies?
Contains hypervariable areas that participate in antigen binding
These areas form a complementary structure to the antigen molecule.
What are Complementary Determining Regions (CDRs)?
Regions within the variable domain that participate in antigen binding
* CDR1
* CDR2
* CDR3
There are 3 CDRs per chain, totaling 6 per binding region.
What stabilizes the beta sheet structure in antibodies?
Disulphide bonds and hydrophobic interactions
The beta strands are arranged into pairs of sheets forming a tertiary structure.
What are the main antibody classes?
IgG, IgA, IgM, IgE, IgD
Each class has different biological functions and structural characteristics.
What is the first class of antibody produced during a primary immune response?
IgM
IgG production follows, with a rapid decrease in IgM.
What is class switching in antibodies?
A genetic rearrangement process allowing B cells to switch from producing IgM to other isotypes
Mediated by AID and influenced by cytokines.
What is affinity maturation?
The process by which B cells produce antibodies with progressively higher affinity for an antigen
Involves somatic hypermutation and selection in germinal centers.
What happens during the lag phase of an antibody response?
B cells make contact with the antigen, proliferate, and differentiate
This phase can last from 3 to 30 days.
What are the functions of antibodies? (List at least three)
- Agglutination
- Neutralisation
- Opsonization
- Activation of Complement
- Antibody-dependent cell-mediated cytotoxicity (ADCC)
Each function plays a crucial role in the immune defense against pathogens.
True or False: IgG is the most common subclass of antibody.
True
IgG1 is particularly prevalent in serum.
What is the significance of somatic hypermutation (SHM)?
Introduces rapid point mutations in the variable region of Ig genes, enhancing antibody diversity and specificity
Occurs in B cells within germinal centers after antigen exposure.
