T cells Flashcards
Where do T cells develop?
Thymus
What receptors does T cell have?
TCR, CD4 and CD8
Which T cells have CD4?
T reg and Th
Which T cells have CD8?
Tc Cells
What does the Treg cell do?
suppresses unwanted immune response and limits response to pathogenesis
What is the structure of TCR?6
Heterodimer
yd or ab (most)
Has variable region and constant region
Has inter and intra chain disulfide bonds
Variable region recognises particular peptide MHC combination (gives spec to TCR)
Binding of MHC TCR, CD4…
TCR binds to MHC +peptide
CD4 or CD8 bind to non polym but of MHC
What is a double positive Tcell
While maturing in the thymus - it has both CD4 and CD8
How does T cell signal inside the cell?
Cytoplasmic bit of TCR is too short, has CD3 alpha beta epsilon gamma and zeta chains (CD3 co receptor complex)
LCK recognises ITAMS on CD3 co receptor
Protein kinases take up phosphate group and add it to tyrosine
Cell signalling cascade and transcription factors activated
What are LCKs and ITAMS?
LCK is a tyrosine kinase associated with the tails of CD4 and CD8
ITAMS - Immune receptor tyrosine based activation motif
Are V regions different in one Tcell?
All the same in one T cell
How is variability created in TCR?
Genetic recombination
What needs to happen after genetic recomb?
Selection in thymus
+ve - recognise own MHC
-ve - Recog peptides from foreign
When does anergy happen?
If only CD4/CD8 and TCR activated
What do we need so that anergy doesn’t happen?
Costimulation
Most important co-stimulatory activities are: 4
CD86 and CD80 interact with CD28 (or CTLA4 to inactivate)
VCAM1 and VLA4
ICAM1 and LFA1
Also need cytokines and soluble mediators
3 Functional Activities of T cells
Proliferate, mediate effector functions, form memory cells
CD4 Th 1 produces
IFNy, IL2, TNFB
CD4 Th1 job
Help CTL and macrophages (and some B)
Inhibit Th2
CD4 Th2 produces
IL4, IL5, IL10, IL13
CD4 Th2 job:
Help B cells, Inhibit Th1
CD4 Th17 produces:
IL17 and IL22
CD4 Th17 job:
Promote inflammation
CD4 Tfh produces
IL21, ICOS
