TCR’s and BCR’s. Flashcards
What is the function of TCR’s and BCR’s?
They help B and T cells to recognise antigens.
What part of a TCR or BCR binds to the epitope of an antigen?
The antigen binding component.
What area of a B or TCR undergoes gene rearrangement?
The antigen binding component.
Why is it important that the antigen binding component can under go gene rearrangement?
As if the genes were pre-destined the genome would be enormous.
What part of a BCR or TCR never undergoes gene rearrangement?
The signalling component.
What is the signalling component of a BCR or TCR involved in?
Signal transduction.
What molecule within a TCR helps with signalling?
CD-3.
What molecule within a BCR helps with signalling?
CD-79.
What is the affinity of a BCR or a TCR?
How strongly it binds to an antigen.
Will there be an immune response if a TCR or BCR binds weakly to an antigen?
No.
What are the binding sites of BCRs and TCRs specific for?
Different antigens.
Can TCRs and BCRs bind to different antigens?
Yes, this is how cross reactivity occurs.
What must occur for an antigen to bind to a TCR?
It must be presented by an MHC-1 or MHC-2.
What kind of peptides are read by TCR’s?
Only linear peptides.
Are TCR’s ever secreted?
No, as they are membrane bound proteins.
Can BCRs or TCRs bind to free antigens?
Only BCRs.
Are BCR’s ever secreted?
They can be secreted as an antibody which is a BCR without the membrane anchor.
Antibodies are always identical to what?
To the BCR on the B cell that made them.
Can BCRs and TCR bind to multiple antigens?
No, they can only respond to one antigen at a time.
Can BCRs and TCR recognise multiple antigens?
Yes.
Why can BCRs and TCRs recognise so many receptors?
Because of gene rearrangement.
What is the difference in antigen binding between BCRs/TCR’s and MHC molecules?
BCRs and TCRs can only bind to a single peptide.
MHC molecules can bind to multiple peptides.
Why are there more B and T cells in the body than MHC molecules?
Because B and T cells are more specific and we need multiple B and T cells to recognise pathogens.
MHC molecules can bind to multiple antigens so 1 MHC can do the work of many B and T cells.
Is the somatic gene rearrangement that occurs in TCRs and BCRs completely random?
Yes, this generates B cells and T cells that have billions of different receptors.
What proteins are essential in the gene rearrangement that occurs in BCRs and TCRs?
RAG proteins.
What are the co-stimulatory molecules that are found on the surfaces of T and B cells?
Additional receptors that are used for B and T cell activation.
They are also used for immunophenotyping lymphocytes.
What 2 cell types have antigen receptors?
B cells.
T cells.
What 3 cell types have antibody receptors?
Natural killer cell.
Macrophages.
Neutrophils.
What stimulates the co-stimulatory molecules on BCRs and TCRs?
Exposure to PAMPs or cytokines.
Are cytokines part of the innate or adaptive immune system?
The innate immune system.
Are co-stimulatory molecules necessary for full B or T cell activation?
Yes.
What happens when co-stimulatory molecules are activated?
They send a second signal which prevents an overreaction of the immune system.
What do the co-stimulatory molecules on B and T cells help to prevent?
Autoimmunity and reactions to benign antigens such as food antigens.
