lecture 35 - T cells Flashcards
Where do T cells arise?
Bone marrow
How does the thymus develop a T cell to maturity?
TCR gene rearrangement
What is the name for immature T cells, or other immune cells, that enter the thymus?
Thymocytes
What occurs during thymus gene rearrangement?
Thymocytes rearrange the genes coding for the variable part of their TCR (T cell receptor)
Why are a huge variety of TCR receptors expressed across the T cells leaving the thymus?
TCR gene rearrangement is essentially random, producing a wide array of receptors that may or may not be useful in identifying specific antigens
What does a TCR recognise?
A specific peptide + MHC
What are the 2 types of T cell co-receptor?
CD4 and CD8
What is the function of a CD4 receptor?
Assists with the docking of the TCR onto MHC-II and peptide
What MHC does the CD4 co receptor aid in the docking of?
MHC-II
What is the function of the CD8 coreceptor?
Assists with the docking of the TCR onto specific peptides and MHC-I.
What MHC does CD8 aid in the docking of?
MHC-I
What is the name given to T cells that have not been activated by MHC/peptide?
naïve
What is the name for activated T cells?
Effector T cells
What are CD4 T helper cells?
T cells with CD4 coreceptors that recognise MHC-II and peptide from endogenous antigens. Activate B cells and release cytokines to activate CD8 T cells.
What is the function of CD4 T helper cells?
Help CD8 T cells become cytoxic by producing cytokines. Help B cells make antibody
What are CD8 cells?
T cells with CD8 co receptors that recognise MHC-I and peptides from exogenous antigens
What do CD8 T cells develop into?
cytoxic T lymphocytes (CTL)
What are CTLs (cytoxic T lymphocytes) derived from?
CD8 cells
What is the function of CTL (cytoxic T lymphocytes)?
Targeted death (apoptosis) of infected cells so they can no longer act as hosts to pathogens, or so cancerous cells cannot further divide.
What is apoptosis?
Orderly, targeted cell death by CTLs
Why must target cell death be orderly?
Random cell lysis would lead to the spilling out of viruses from inside the diseased cell, allowing them to spread to and infect other cells.
What are memory cells?
T cells that reside in the body for long periods of time until a relevant pathogen is detected, at which point they can rapidly form effector T cells.
What are the two key types of memory T cells that reflect their potential function?
CD4 and CD8 memory T cells.
Why does the body produce memory T cells?
To allow the adaptive immune response to kick in rapidly when a familiar threat is identified, rather than having to go through the slower process of turning naïve T cells into effector T cells.
How are CTLs activated?
By cells that display peptides that match the CTL, as well as MHC-1
