T-Cell Mediated Immunity -- Regulation and Termination Flashcards
How do antigens get to the lymphatics?
Dendritic cells take up bacterial antigens in the skin and move to lymphatic vessels.
DCs with antigen enter the noce and settle in T-cell areas.
Following exposure to antigen, dendritic cells will transition from…
phagocytic to antigen presenting.
How are endocytosed bacteria typically presented?
MHC Class II
How can viral antigens spread from one dendritic cell to another?
Vesicle Fusion
How do antigens that cross present viruses after phagocytic uptake get presented?
MHC Class I
How do antigens get to Ts from skin infection?
Dendritics pick up, undergo maturation, and migrate to periph. LN
How do antigens get to Ts from the blood?
They get trapped by DCs in the spleen
How do antigens get from the mucosal tissues to the Ts?
Collected in tonsils, peyer’s patch, appendix, mesenteric LN
How do native T cells get into LNs
High Endothelial Venules or Upstream LNs
What lets Naive Ts hold onto HEVs?
L-selectin
What happens to naive T cells who enter a node and don’t match anything on?
They hit the efferent lymphatic vessel and move on
Four steps in T cell homing process?
Rolling
Chemokine
Firm Adhesion
Diapedesis/Extravasation
What bonding occurs in the rolling stage?
L-Selectin (tcell) binds onto host Gly-CAM-1 and CD-34
What boding occurs in the chemokine phase?
CCR7 + SLC/ELC
What bonding is important in the firm adhesion stage?
LFA-1 binds onto integrins (es. ICAM-1)
CD4 T cell LFA-1 binds…
ICAM1/2
CD4 T cell CD2 binds…
LFA-3
CD4 T cell CD4 binds…
MHCII
CD4 T cell TCR/CD3 binds…
MHCII/Peptide
CD4 T cell CD28 is required for…
B7-1/B7-2
TCR/CD3:MHCI binding activates….
T Cell through PIP/DAG/IP3
Value of integrins?
TCR/MHC requires its stability
Both directly and indirectly enhances T Cell Reaction
Which integrins are on the T cell?
ICAM-3, CD2
Relationship of TCR/MHC and LFA-1 bond?
- Weak bond btw T’s LFA and DC ICAM-1
- Stabilizes TCR MHC bond
- Bonding signals LFA-1 conformational change that increases affinity and prolongs contact.
Most important co-receptor bond?
T cell CD 28 must bind to DC B7
B7 can bind to what two molecules (with what purpose)
CD28 (Initiation)
CTLA4 (Termination)
Who expresses CTLA4?
Activated Ts
Three cytokines important for DC maturation.
TNF-alpha
IL6
IFN-gamma
What happens when TCR activation happens without CD28?
Anergy
Can cells return from anergy?
No
Who expresses B7?
Only Pro Antigen Presenting cells
DCs, B Cells, Macrophages
Which cells are most important for turning Ts on?
DCs
How are antigens picked up by the three types of APCs?
DCs - Macropino+Phago
Macro - Phago
B Cells - Ig Receptor
Other than LNs, where can the APCs be found?
DC - Connective Tissue + Epithelium
Macro - Connective Tissue+ Body Cavities
B Cells – Peripheral Blood
DCs are good at presenting…
Bacterial and Viral Antigens
Macrophages are good at presenting….
Extracellular Bacteria
B cells are good at presenting…
Soluble Antigen
What induces dendritic cell maturation?
Bacterial products such as LPS, Cell Wall, and Cytos like TNF-alpha