L17 - T Cells - Cellular Interactions and Trafficking Flashcards
What draws T cells into the T Cell zone?
CCR7 on the surface of T-Cells (and dendritic cells) interacting with CCL19/21
What enhances priming capacity of dendritic cells from T cells?
CD40L (T-cells) binding to CD40 on dendritic cells and other antigen presenting cells
What are the four steps for entry of naive T cells into lymphoid tissues?
- Rolling
- Activation
- Adhesion
- Diapedesis
Explain the rolling step and the role of L-selectin
L-selectins (CD62L) expressed on the surface of naive T cells acts as a homing receptor to enter secondary lymphoid tissues
- Only strong enough to slow down the cell
What ligands can L-selectin bind to?
GlyCAM-1 - HEV of lymph nodes
CD34 - endothelial cells
MadCAM-1 - endothelial cells of gut-associated lymphoid tissues
Explain the adhesion step and the role of LFA-1
LFA-1 is an integrin expressed on T-cells. Binds to ICAM-1 enabling it to squeeze in between cells
What is the importance of IL-2?
Key growth factor for responding T-cell
- Entry into cell cycle requires IL-2
What are the two affinities for IL-2 and what chains make these up?
- Moderate affinity. gamma and beta chain
- High affinity. alpha, beta and gamma chain
What is CD69?
A retention signal. Goes down with every T-cell division
What is S1P1?
Exit Signal
What is the interaction between CD69 and S1P1?
Exit signal (S1P1) can form a dimer with CD69. If lots of CD69, lots of S1P1 bind, get internalized and degraded. Exit signal is actively degraded in presence of CD69. As T-cells replicate and CD69 “concentration” is less and less, balance is altered and exit signal prevails