T cell Mediated Immunity Flashcards
What is present on a Mature Naive T cell
CD4+ or CD8+ CD28+ MHC/HLA class 1 TCR complex including CD3 molecules and Zeta LFA-1 and VLA -4 adhesion molecules Chemokine receptor CCR7
Where does T cell activation occur
Lymph organs
by Dendritic cells
What activates Memory T cells
B cells and Macrophages and Dendritic cells
Who activates B cells and Macrophages
CD4+ T cells
What happens in the process of activation of DCs
once a peripheral DC is activated itloses its adhesive markers and up regulates CCR7
Increses expression in MHC/HLA and CD80 (B7)
Travel to the secondary lymphpoid tissue and they mature as they migrate
Finally they present Ag to T cell
How do the Naive T cell migrate into the Peripheral Lymphoid organ
go across the High endothelium venules (HEV) in the cortex
L selectin
L selectin ligand
Naive T cells
Initial weak adhesion to naive T cells to the high endothelial Venule in lymph node
LFA-1
B2 Integrin
binds ICAM-1
Stable arrest on HEV
CCR7
on Naive T cell
binds CCL19 or CCL21
Activation of integrins and chemotaxis
E and P selectin ligand
Found on Effector T cells
binds E and P selectin on Endothelial
Initial weak adhesion of effecto and memory T cell to cytokine activated endothelium at peripheral site of infection
LFA-1
VLA-4
B2 and B1 integrin respectively
binds ICAM or VCAM on endothelial cell
Stable arrest on cytokine activated endothelium at peripheral site of infection
CXCR3
on Effector and activated T cell
binds CXCL10
activation of Integrins and chemotaxis usual in the direction of the follicle wear the B cell is located
Surface molecules of T Lymphocytes: CD3
signal transduction by TCR complex
Surface molecules of T Lymphocytes: Zeta
Signal transduction by TCR complex
Surface molecules of T Lymphocytes: CD4
SIgnal transduction
binds to Class II MHC on antigen presenting cells
Surface molecules of T Lymphocytes: CD8
signal Transduction
Binds to Class I MHC presented on all nucleated cells
Surface molecules of T Lymphocytes: CD28
Signal transduction (costimulation)
Binds B7-1/B7-2 on antigen presenting cell (CD80)
Surface molecules of T Lymphocytes: CTLA-4
Inhibition signal
Binds B7-1 and B7-2 ligands on Antigen presenting cells
Surface molecules of T Lymphocytes: PD-1
Inhibition signal
Binds to PD-L1/PD-L2
on antigen presenting cells, tissue cells, and tumor cells
Surface molecules of T Lymphocytes: LFA-1
Adhesion signal transduction
Binds ICAM-1
on Antigen binding cells and endothelium
what happens to integrins when there is TCR/HLA antigen recognition
Changes its affinity from low to high
causes clustering and makes a strong T cell and APC adhesion leading to a strong T-cell response
What is the First Signal of the T cell activation
Binding of the MHC/peptide complex to the TCR
What is the second signal to get a T cell activation
Co stimulatory molecules:
CD40L on T cell binds to the CD40 on the APC
B7 binds to CD28 on the T Cell and then cytokines are released and taken in by the T cell (IL-12)
What Cytokine is released from the APC and taken up by the naive T cell
IL-12 to enhance T cell proliferation and differentiation
T cell activation signal cascade
LcK activates the ITAM and tyrosine kinase ZAP-70
THis activates PLCy, Ras, Rac, and PI3
PLCy increaseds cytocolic Ca2+ and DAG which produces calcineurin and PKC
RAS and RAC in its GTP form activate ERK and JNK
PI3 kinase activates PIP3 and akt and mTOR
All of these produce NFAT and NFkB and AP-1 which increases protein synthesis
