Lecture 5 Flashcards
(55 cards)
What is the CMI?
Cell mediated immunity
What are the functions of CD4+ and CD8+ cells in CMI?
CD4s recruit and activate phagocytes to kill ingested and some extracellular microbes
CD8s kill cells harboring microbes in cytosol, eliminating reservoirs of infection.
What do Th1s secrete?
What do Th2s secrete?
IFNgamma
IL-4, 5, and 13
What are the three signals required for T cell activation/differentiation?
Ag presentation, co-stimulatory molecules, and cytokines.
What do each of the three required signals for T cell activation do for the T cell?
Ag presentation activates the T cell
Co-stimulation allows the T cell to survive
Cytokines allow the T cell to differentiate into what’s req’d
Which T cell can respond to their target without co-stimulation?
Effector T cells
Which T cell homing receptors are on naive T cells?
L-selectin, LFA-1, and CCR7
Which T cell homing receptors are on activated effector and memory T cells?
E- and P- selectin ligand, LFA-1, VLA-4, and CXCR3, etc.
What does LFA-1 and its receptor ______ do for the T cells?
LFA-1 and ICAM-1 allows the stable arrest on high endothelial venules - allows T cell to stop in lymph node
What does L-selectin and its receptor _______ do for the T cells?
L-selectin and L-selectin ligand allow adhesion of T cells in high endothelial venules in lymph node
Which two receptors allow T cells to stick to HEVs in lymph nodes to be activated?
LFA-1 and L-selectin
Through what do naive T cells migrate to enter lymph nodes?
What do naive T cells express that mediate their selective migration into lymph nodes?
High endothelial venules
They express L-selectin (CD62L) and the chemokine receptor CCR7
Why do effector T cells migrate to the sites of infection?
They express adhesion molecules and chemokine receptors that bind to ligands expressed/displayed on vascular endothelim in response to inate immune responses to microbes.
Describe in brief the homing of effector T cells to a site of infection.
CTLs have adhesion molecules/chemokine receptors that bind to ligands in site of infection. Their homing is independent of Ag recognition but those that do recognize the Ag are preferentially retained/activated at infection site.
What is S1P?
S1P is phospholipid sphingosine 1-phosphate which regulates entry /exit of T cells through lymph nodes
Describe how S1P regulates T cell migration.
Levels of S1P are higher in the blood/lymph than inside lymph nodes.
Before T cells are activated (w/o Ag stim) they have a high expression of S1P receptor so exit LN.
If Ag stim present they suppress their S1P expression for clonal expansion inside LN.
How do T cells exit the LN after Ag stim?
They lose expression of L-selectin, CCR7, and re-express S1P to leave the LN.
What allows T cells to travel to the LN?
CCL5 is expressed higher in the LN and attracts T cells
What are the secondary lymphoid tissues?
Lymph node
Spleen
Peyer’s patch
Where are most DCs located?
In secondary lymphoid tissues - resident DCs
How do DCs migrate from secondary tissues to the lymph nodes?
They activate their CCR7 receptor and travel to the LN in tandem with the T cells
How do DCs mature to become APCs in peripheral tissues?
DCs encounter MAMPs and are activated
TLR signaling induces expression of CCR7 and enhances processing of pathogen antigens
CCR7 directs DCs to migrate to LN and ups their co-stim molecules & MHC molecules
Activated DCs in T cells zones prime naive T cells
What are CTLs specialized for?
The killing of cells infected in INTRAcellular pathogens
How do CD4 and CD8s interact?
How does this work?
Which receptor/molecule is used?
CD4 cells help drive CD8 T cell responses
CD4+ cells can activate APCs further so they can better activate CD8+ cells
4-1BBL is a ligand on APCs that further activates CTLs
