APC's. Flashcards
What is the function of APC’s?
To acquire and present exogenous antigens to CD-4+ T helper cells.
What are the 3 3 types of professional APC?
Dendtritic cells.
Macrophages.
B cells.
Will an infected cell that presents an antigen presents an antigen to the immune system be considered to be an APC?
No.
What can all antigen presenting cells present antigens to?
An MHC-2.
What is the only APC whose entire role is antigen presentation?
Dendritic cells.
What is the best APC?
Dendritic cells.
What 3 tissues are dendritic cells not found in?
The brain.
The testes.
Some parts of the eye.
What cells are responsible for antigen presentation in the brain, the testes and some parts of the eye?
Macrophages.
What is the main role of B cell?
To make antibodies.
What receptor is found on a B cell?
A B cell receptor which binds to antigens.
What molecule is expressed on the cell surface of APC presenting cells?
MHC-2 molecules.
What cells express a very high amount of MHC-2 molecules on their cell surface?
Dendritic cells.
What cells express the highest amount of MHC-2 molecules?
Dendritic cells.
Can macrophages present any antigen?
No, they must be stimulated before they can present antigens.
What is the only cell that macrophages can present antigens to?
Sensitised T helper cells which are T cells that have seen antigens before.
What 2 cell types can dendritic cells present antigens to?
Naive T cells.
Sensitised T cells.
Can T cells bind to any antigen?
No, the antigen must be bound to an MHC molecule.
What kind of antigens are presented by an APC?
Exogenous antigens.
What are the 3 things that can bind to an epitope?
A TCR from a CD4 or CD8+ T cell.
A BCR.
An antibody.
What is the best antigen presenting cell?
A dendritic cell as they are the only full time antigen presenters.
What are the only APC’s that can stimulate a naive T cell?
Dendritic cells.
What happens once an antigen has been presented to a naive T cell?
It becomes a sensitised helper T cell.
How do immature dendritic cells become mature?
They sample their environment and capture antigens to become mature.
Where are mature dendritic cells found?
In the lymph tissue.
What do dendritic cells present antigens to?
Naive T cells.
Where are dendritic cells found in greatest numbers?
The lymph nodes, skin and mucosa.
What is the only antigen presenting cell that can present antigens to naive T cells?
Dendritic cells.
Why are dendritic cells essential for activating primary immune responses?
Because they are the only cells that can present antigens to naive T cells.
Where are dendritic cells produced?
In the bone marrow.
What do dendritic cell use to present antigens to helper T cells?
A MHC-2 molecule.
What are the 3 major classes of dendritic cells?
Thymic dendritic cells.
Interdigitating dendritic cells.
Langerhans dendritic cells.
What is the role of thymic dendritic cells?
They educate T cells to recognise self antigens.
What happens to T cells that do not recognise self antigens?
They are killed.
What are interdigitating dendritic cells?
Mature dendritic cells which interact with T cells in the lymph node.
What are Langerhans dendritic cells?
Immature dendritic cells that are found in the skin.
Are macrophages good APCs?
They are quite good, mainly because they must be activated before they can present antigens.
What cells will macrophages present antigens to?
To specialised T helper cells.
Macrophages are the only APC in what 3 tissues?
The brain, the testes and they eye.
When will B cells make an antibody?
When they have received antigens.
What receptor is found on B cells?
A B cell receptor (BCR) which is a membrane bound antibody.
What antigens can a BCR bind to?
Any antigen, not just protein antigens.
How do B cells acquire antigens?
By being specific for certain antigens.
This means that one B cell will have specificity for a particular antigen.
How does a B cell acquire an antigen?
It uses its BCR to bind to an antigen.
It then ingests it and processes it.
It gives the peptide to an MHC-2 which can present it to a helper T cell.
What happens when a B cells BCR binds to an antigen?
The B cell differentiates into an antibody secreting cell known as a plasma cell.
What cells help a B cell differentiate into a plasma cell?
Helper T cells.
What kind of antibodies are made by B cells?
Antibodies that mimic the antigen that is bound to the BCR.
