T-Cells Flashcards
Where do T-cells Develop?
Thymus
Stages of T-cell Development?
Haematepoetic precursor - Lymphoid progenitor - DN1-DN2 - DN3 - DN4 - DP - CD8/CD4 DP - CD8 SP/CD4 SP (positive selection) and emigration to periphery or Death (negative selection)
T-cell Development
1) DN gives rise to AlphaBeta or yo T-Cell reseptor (TCR) expressing cells
2) Pre-TCR alpha pairs with TCRbeta chain
3) TCRbeta chain is a product set somatic DNA re-arrangement requiring RAG1 and RAG2
4) Pre TCR AlphaBeta pair then assosiate with CD3/2 complex
5) TCRalpha locus recombination occurs to produce mature AlphaBeta antigen receptors
6) Thymocytes start expressing CD8 and CD4
What are the 5 T-Cell lineages and their pathways once their activated?
1) IL-6 binds to STAT3. STAT3 phosphorylated and enters nucleus. Bcl6 Activated to produce TfH cells. TfH cells release IL-21 Cytokines.
2) IL-4 binds to STAT6. STAT6 eneters nucleus and activates GATA3. GATA3 produced Th2. Th2 cells release IL-4/IL-13
3) IL-12 binds to STAT4. STAT4 activates Tbet which produces Th1 cells. Th1 cells release INFgamma
4) IL-6/IL-23 bind to STAT 3. STAT3 activates RoryT which produces Th17 cells. Th17 cells release IL-17alpha/IL-17f
5) IL-2 Binds to STAT5. STAT5 activates FoxP3 which produces iTregs. iTregs release IL-10, IL-35 and TGFbeta
How are T-cell linages induced?
Cytokine binds to TCR (eg IL-12 binds to IL-12R on T-cell).
This activates STAT via phosphorylation (Eg STAT5 for IL-12)
STAT enters nucleus and activates master transcription factor
Whats the role of Th Responses?
1) TfH- B-cell help
2) Th2- Helminths/parasites
3) Th1 - Intracellular Pathogens
4) Th17 Extracellular Pathogens
5) iTregs - Tolerance
T-Cell differentiation measurements
Flow-cytometry to asses transcription factors and cytokine profiles
Flow allows phenotype detection of individual cells
Use Fluorescent anitbodies to bind to Cytokines and Master transcription factors
How do CD4 T-Cells function through positive and negative stimulatory pathways?
Positive:
MHC/Peptide binds to TCR (signal 1)
Co-stimulatory ligand binds to co-stim receptor (signal 2)
-This results in: Proliferation/Cytokine secretion, T-cell differentiation, Prevention of Anergy/Apoptosis
Negative: Negative co-stim receptor (eg PDLA1 or CTLA-4) bind to complimantary receptor
-This results in anergy/apoptosis
What are the CD28 family of T-cell co receptors?
CD28, CTLA-4, ICOS, PD1, BTLA
What are the TNFR family of T-cell co-receptors?
HVEM, CD27, OX40, 4-1BB, CD30
What is the CD2 T-cell co-receptor?
CD2
What are the 3 signals in T-cells
Signal 1 - MHC II binding with TCR
Signal 2 - Co-stimulatory binding with T-cell co-stimulatory receptor
Signal 3 - Cytokine - T-cell cytokine receptor
Jak Kinase and Cytokines of IL-2 common gamma chain
1) IL-2 common gamma chain signal thorough Jak kinase and activate cell survival/proliferation
2) Inhibiting Jak can inhibit STAT phosphorylation
3) Inhibiting STAT (eg STAT5 With ToTa) you can visulise STAT using flow cytometry but you WONT see phosphoSTAT
What is Functional Plasticity in T-CELLS?
1)Th Cells can loose their master transcription factor and replace it with another MTF, then become that correlating
T-Cell. Eg Th17 loosing RoryT, gaining FoxP3 and becoming a iTreg
2) This can occur when there is a high burden for a specific type of T-Cell Ie Th17 needed to attack extracellualr bacteria
3) This is also called FATE MAPPING
How can you visualise Functional Plasticity?
1) You can stain master transcription factors with monoclonal fluorescent antibodies to get them to emmit a specific colour i.e RED
2) When T-cell shift Master transcription factors, it will loose this fluorescence and you can use flow to look at tjis swap
3) Eg it is possible for Th1 cells to loose Tbet, gain FoxP3 and shift to Tregs
