Epitopes. Flashcards
What are epitopes?
The piece of an antigen that is recognised by the receptors on the antibodies, T cells or B cells.
Can TCRs directly recognise an epitope?
No, the epitope must be presented to them by an APC.
Do MHC molecules recognise epitopes?
No, they simply bind to them and then display them to a T cell.
What happens once MHC molecules present an antigen to a T cell?
The T cell recognises the antigen and stimulates an immune response.
Can an immunogenic molecule have multiple epitopes?
Yes, this allows multiple immune cells to respond to that pathogen.
Protein epitopes will be within what structure of the protein?
The primary, secondary, tertiary or quaternary structure of the protein.
What are conformational protein epitopes?
When they are in their native conformation.
What are linear protein epitopes?
When they are a basic polypeptide chain.
What kind of epitopes can be recognised by TCR’s?
Linear epitopes as it is only a small polypeptide chain that is presented to them.
How many amino acids can be recognised by a TCR?
A chain of 8-24 amino acid sequences.
What kind of epitopes can be recognised by BCR’s?
Conformational and linear epitopes.
When will cross reactivity occur?
When you have similar epitopes that come from different sources.
How does cross reactivity occur?
When antibodies that are supposed to detect one antigen attack another antigen that is similar to the original antigen.
What name is given to the process when the same antigen binds to multiple epitopes?
Cross reactivity.
What is an example of cross reactivity?
When brucella abortis is confused for yersinia enterocolitica.
Yersinia enterocolitica causes a cow to make antibodies that cross react with brucells abortis.
This means the cows will test positive for brucella abortis.
How can microbial epitopes trigger autoimmunity?
As they look similar to self antigens and this can trigger an autoimmune response.
What are natural antibodies?
Antibodies in the body that can attack the antigens of pathogens which the body has never encountered before.
Are natural antibodies in the body because of a vaccine?
No.
What are 2 things that can cause natural antigens?
Cross reactions to harmless bacteria or food antigens.
What is a good example of cross reactivity in animals?
Blood antigens. E.g. People with type A blood antigens will not be able to tolerate type B blood antigens in their body.
What 2 animals cannot generate natural antibodies against RBCs?
Dogs and horses.
What 3 animals can generate natural antibodies against RBCs?
Humans, cats and pigs.
Why should we be concerned about blood transfusions in animals that can generate natural antibodies against RBCs?
As they can mount immune responses against the transfused red blood cells.
What are haptens?
Antigenic molecules that are too small to be immunogenic.
What happens if a hapten binds to a BCR or a TCR?
They will not stimulate an immune response.
When can a hapten trigger an immune response?
When the hapten is bound to a carrier protein.
When can a hapten be recognised by a TCR or a BCR?
When the hapten is bound to a carrier protein.
What is a drug that is a hapten?
Penicillin.
When can penicillin cause an immune response?
When it is bound to albumin.
When will complement proteins and antibodies bind to antibodies with much higher affinity?
When the antibodies are bound to an antigen.
Why is it good that complement proteins and antibodies bind to antigen bound antibodies with much higher affinity?
So that they don’t randomly bind to antibodies and cause an unnecessary immune response.
