🌞 T Cell Activation and Differentiation Flashcards
(11 cards)
What are the three signals required for T cell activation?
1: TCR:MHC/Ag peptide
#2: costimulation → CD28:B7(CD80/86)
#3. Ck signalling → guide T cell diff into subsets (Th1, Th2, Th17)
What happens if T cells receive signal 1 but not signals 2 or 3?
No signal #2 → T cell becomes anergia (non-responsive) →app (peripheral tolerance mechanism)
No signal #3 → T cell X diff into subsets → weak/incomplete effector re
What is co-stimulation and why is it important?
signal #2 → CD28 on T cell binds B7 (CD80/86) on APC
peripheral tolerance mechanism → ensures T cell X re: self Ag
What cytokines influence T cell effector differentiation?
IL-12 → TH1
IL-4 → TH2
IL-6, TFG-b → TH17
IL-2 → Treg
IL-21 → TFH
How do dendritic cells activate naive T cells?
DCs = APCs → pres exogenous Ag pep frags → naive CD4+ T cell → bind TCR = signal #1 in T cell activation
also pres endogemous ag pep frags → naive CD8+ T cells (like all nucleated cells)
What is the immunological synapse?
interface bw naive T cell + APC presenting Ag on MHC
What is the function of CD28 and B7 in T cell activation?
signal #2
peripheral tolerance mechanism
ensures T cell able to receive prolific + diff signals → appropriate effector re
What cytokines promote Th1and Th2?
IL-12 → TH1
IL-4 → TH2
What is the function of Th1 cells?
prod IFN-g →
- active MPs → inc phag
- stim b cells → prod IgG → opsonisation + c’ activ
What is the function of Th2 cells?
- prod IL-4 → stim B cells → IgE → binds MCs
- prod IL-5 → activ eosinophil
- prod IL-13 → inc mucus prod, expels parasites, promos tissue repair
What is the function of Th17 and Treg cells?
TH17 → prod IL-17 → recruit Ns + promo inflamm
Treg → modulates IR during infection → prev autoimmunity + maintain immune homeostasis
