T Cell Activation. Flashcards
What are the 2 signals that can activate a T cell?
Signal 1.
Signal 2.
Where does signal 1 for T cell activation originate from?
A CD3 molecule on a T cell.
How do co-stimulators help with T cell activation?
They induce a response as the binding of a TCR to an MHC is not enough to induce a response on its own.
When are co-stimulatory molecules produced?
When an APC comes into contact with a PAMP or when a T cell binds to an APC or MHC.
What other molecule is produced when a T cell binds to an APC that is bound to a PAMP?
A co-stimulatory molecule.
An MHC bound to a foreign peptide can be described as what?
An APC.
Which interleukin is incredibly important for T cell activation?
IL-2.
What happens to T cells once they have been activated?
They proliferate.
Why is IL-2 needed for co-activation?
It is a safety mechanism that prevents autoimmunity.
What happens if IL-2 is not present during T cell activation?
The T cell cannot enter the cell cycle and replicate.
Is IL-2 necessary for T cell activation?
IL-2 must be present for proliferation to occur.
What happens when signal 1 is activated during T cell activation?
The naive T cell interacts with an MHC via its CD4 molecule.
CD-3 is activated and sends a signal which activates the T cell.
What happens when signal 2 is activated during T cell activation?
Co-stimulatory molecules trigger the T cell to enter G1.
IL-2 is transcribed and proliferation can occur.
What are the 2 types of co-stimulator for T cells?
CD40 ligand.
CD-80/B7.
When will CD-40 ligand and CD-80/B7 be expressed?
In the presence of PAMPs bound to a PRR.
This causes an up-regulation of both co-stimulatory molecules.
What triggers T cells to up-regulate its production of co-stimulatory molecules?
An MHC binding to the T cell.
Will PAMPs stimulate the production of co-stimulators on an APC or a T cell?
On the APC.
Will TCR stimulate the production of co-stimulators on an APC or a T cell?
The T cell.
Can TCRs bind to PAMPs?
No, as they do not have PRRs.
Why is it best that antigens come from bacterial proteins?
As we can break them into peptides that can be read by a T Cell.
Why do we want to have signals that inactivate T cells?
As we do not want cytokines to be produced the whole time.
What cells always present antigens to T cells?
An MHC.
