Lecture 4 - Antibody basics Flashcards
Immunogen
A substance which stimulates a specific immune response
Antigen
A substance which is the target of an immune response
Antibody
A serum protein that binds to antigens, made by B lymphocytes
Determinant or epitope
Antibody binding-site on antigen
Three most common antigens on influenza virus
Haemagglutinin
Neuraminadase
M2 ion channel
Does any antigen binding on a BCR stimulate the B cell?
Not necessarily
What is the requirement of antigen binding on BCR to stimulate the B cell?
BCR clustering and oligeromisation is required.
This is achieved when many antigens are bound to a carrie, causing them to be close together.
Can parts of an antigen or antigen-binding site be changed?
Yes, if the change is minor.
EG: Changing an uncharged amino acid for another uncharged amino acid might have little effect
Example of a hapten
Dinitrophenyl
What is a hapten?
Small, organic molecule that is attachable to larger structure.
Is not immunogenic by itself, but stimulates immune response when bound to a carrier.
Common hapten structure
Polyamino acid
Poly-lysine
What is a carrier?
Usually a protein
Minimum size required for crosslinking of BCR, T cell antigens
Haptens bind to carrier
Necessary for an adaptive immune response
What must a hapten do to stimulate an immune response?
Be covalently linked to a carrier
Interactions involved in antibody binding 1) 2) 3) 4)
1) Electrostatic
2) Hydrogen bonding
3) Hydrophobic/hydrophilic
4) Van der Waals forces
Difference between linear and conformational epitopes
Conformational recognition dependent on epitope being in native conformation.
Conformational can only be recognised by antibodies
Linear epitopes can be recognised in denatured proteins.
Linear epitopes recognisable by both antibodies and TCR
Three main types of antibodies against an immunogen
1) Anti-hapten
2) Anti-carrier
3) Anti-hapten/carrier complex
Way to strengthen anti-hapten response
Immunise first with hapten/carrier complex.
Immunise after with same hapten, complexed to a different carrier.
What is antisera?
Blood depleted of red blood cells
Contains multiple antibody types
When is cross-reactivity possible?
When an epitope is conserved
What is serology?
Using antibodies to determine structural relatedness of antigens
What are the limitations of TCR recognition?
Can only recognise linear, peptide epitopes
