Lecture 21: Cellular Interactions and Trafficking - T Cells Flashcards
Recall the key learning objectives of cellular interactions and trafficking - T cells.
What is the function of HEV?
HEVs enable lymphocytes circulating in the blood to directly enter a lymph node (by crossing through the HEV).
Naiive T cells circulate through _______________. Naiive T cells are fully developed T cells found in ____________ that haven;t been activated by __________________.
Naïve T cells circulate through lymphoid organs. Naïve T cells are fully developed T cells found in lymphoid organs that have NOT been activated by cognate antigen
____________ increases the chances of naiive T cells encountering the ‘correct’ DC that present their specific antigen. The cycle is estimated to be performed in about ______. If no antigens is encountered, the naive T cell depart via _________________.
Describe selectins.
Describe integrins.
L-selectin (CD62L) binds to _________, such as _______________, ________________, and _______________.
GlyCAM-1 (HEV), CD34 (endothelial cells), and MadCAM-1 on endothelial cells in gut-associated lymphoid tissues.
LFA-1 (CD11a:CD18) binds to _______.
LFA-1(CD11a:CD18) binds to ICAM-1; as the cell moves along it makes new contact with additional ICAM-1 molecules, enabling it to squeeze through in between cells
Describe the entry of Naiive T cells into lymphoid tissues.
Migration of naive T cells into secondary lymphoid tissues depends on their binding to high endothelial venules (HEVs) through cell-cell interactions that are not antigen-specific but are governed by cell-adhesion molecules.
Naiive Tcells enter through HEV in the paracortex. By responding to CCL19-21 via CCR7. they are attracted towards DC and will probe it for antigen.
Naiive T cells are attracted to the T cells zone via _________ chemokines, by binding to ______.
Naiive T cells are attracted to the T cells zone via CCL19/21 chemokines, by binding to CCR7.
Briefly describe DC.
Recall how CD4+ T cell can assist in the activation of CD8+ T cells.
In the majority of viral infections, CD8 T-cell activation requires additional help, which is provided by CD4 effector T cells. CD4 T cells that recognize related antigens presented by the antigen-presenting cell can amplify the activation of naive CD8 T cells by further activating the antigen-presenting cell.
B7 expressed by the dendritic cell first activates the CD4 T cells to express IL-2 and CD40 ligand. CD40 ligand binds CD40 on the dendritic cell, delivering an additional signal that increases the expression of B7 by the dendritic cell, which in turn provides additional co-stimulation to the naive CD8 T cell. The IL-2 produced by activated CD4 T cells also acts to promote effector CD8 T-cell differentiation.
Other than that, CD4 T cell binding with resident DC also assist in amplifying the effector response of DC cells to IFN, assisting in the activation of DCCD8+ T cell.
Recall the three signals required for naiive T cell activation.
Recall the expression of IL-2R in T cells.
Activated T cells secrete and respond to IL-2. activation of naive T cells induces the expression and secretion of IL-2 and the expression of high-affinity IL-2 receptors. IL-2 binds to the high-affinity IL-2 receptors to enhance T-cell growth and differentiation.
___ as key growth factor for responding T cells. It also is required in the ______________.
Activation of naive T cells induces the expression and secretion of IL-2 and the expression of high-affinity IL-2 receptors. IL-2 binds to the high-affinity IL-2 receptors to enhance __________ and _____________
Activated T cells secrete and respond to IL-2. activation of naive T cells induces the expression and secretion of IL-2 and the expression of high-affinity IL-2 receptors. IL-2 binds to the high-affinity IL-2 receptors to enhance T-cell growth and differentiation
Integrins also play an important role in the formation of ________________ between __________ and _______.
___________ license DC to improve their ability to stimulate __________________.
Recall how activated T cells depart the lymph node.
The activation sequence of naIive T cells actively prevents exit, because elevated CD69 expression prevents S1P receptors upregulation. Only when the activated cells have proliferated and downregulated CD69, will enough S1P receptor remain on their surface and guide them out of the lymph node (‘exit signals’)
