Antibodies Flashcards
What is the name for the region of an antibody above the hinge, comprising of the light chain and two domains of the heavy chain?
FAB = Fragment Antigen Binding
it’s one variable and one constant domain of each of the heavy and light chains
What is the name for the region of the antibody below the hinge, comprised of one constant region of each heavy chain?
Fc = Fragment crystallisable region.
What is the difference between the variable and constant domains of the antibody?
Each of the heavy and light chains has one variable domain on the end, which has the antigen binding site. The shape of the antigen binding site varies between antibodies as each antibody is specific to an antigen.
The rest of the heavy and light chains are constant domains that are the same for each antibody.
How many polypeptide chains make up each antibody?
4.
What is avidity?
Overall strength of the binding between antibody and antigen.
How is avidity increased?
By joining the monomer antibodies together with j chains to form a multimeric antibody. This increases avidity because the number of antigen binding sites are increased.
Multimeric antibodies are more efficient at activating complement.
What is the difference between antigen and immunogen?
Antigen is something that binds to an antibody, immunogen is something that triggers an immune response.
What is class switching?
The antibody can bind to the antigen but it needs to change its function, so it changes the Fc region and maintains the variable domains which are in the FAB region. This means the antibody changes class, e.g changing from an IgG to IgE.
What is affinity?
How well the antigen binding site can bind to the antigen.
What is the difference between the parts of the antigen bound to by antibodies and by T cell receptors?
Antibodies bind to conformational epitopes, which are the overall outside shape of the antigen. T cell receptors bind to linear epitopes, which are the parts of the antigen molecule from inside the antigen, which have been broken down and presented by the Major Histocompatibility Complex.
There are two many different antibodies for there to be one gene for each in the genome, name the three ways the body ensures enough different types of antibodies can be formed.
- Germline diversity of genes (lots of different genes to be combined)
- Combinatorial diversity (the gene segments can be combined differently)
- Junctional diversity (different spaces can be put between the gene segments)
Name the process where different gene segments are combined to code for the antibody.
Somatic recombination.
Name the process where there is programmed mutation of the variable regions of immunoglobulin genes, so the immune system can adapt to new foreign elements that confront it.
Somatic hypermutation.
What is the risk with hypermutation?
Mis-targeted hypermutation can lead to B-cell lymphomas.
Which is the class of antibody that can cross the placenta, and so provides the foetus with passive immunity?
IgG.
