10 – Linking Innate & adaptive: Traveling to lymphoid tissues Flashcards
DCs travel from … to…
from site of infection to lymphoid tissue
Activated DCs travel via … to…
via lymphatic vessel to closest lymph node
Leaves site of infection
Activated DCs express… to…
express receptors that target them to lymphoid tissue
Antigen presentation
Once in lymph node:
Activation of CD4 (Th) and CD8 (Tc) T cells
APCs actiavte T cells through 3 signals:
Activation – pMHC:TCR
Survival – costimulation
Differentiation – cytokines
once DC is activated: what is increased…
Increase expression of receptors & adhesion molecules:They target DC to lymphatics & lymphoid tissues (migration – to let T-cells know)
Increase processing of antigen to present on MHC molecules
Induced expression of co-stimulatory molecules – signal 2 of T cells
Increased expression of MHC molecules
-Increase expression of MHC & antigen processing will increase the # of MHC:peptide combinations
activated DC in lymph node– capable of
priming naive T cells specific to them
Priming: 1st contact that T cells specific to an antigen
Inactivated DC – immature
May dendrites
Can phagocytose
Cover many surfaces to see if needs phagocytose
Activated DC in lymphatic vessel
No longer phagocytic
Increase receptors/adhesion
Activated DC in lymphoid tissue – lymph node
Express peptide:MHC & costimulatory molecules
Interacts with T cells
2 Different types of DC
Conventional dendritic cell – cDC
Plasmacytoid dendritic cell – pDC
explain cDC
Travel to lymphoid tissue once activated
Activate T cells in lymphoid tissue
Classic APC
explain pDC
High levels of PRRs
Can produce large amounts of type I IFN –potent antiviral cytokine
Stay at site of infection
Secrete cytokines & can amplify local response
steps of Activated DC travels to lymph node
1.PRR signaling –> phagocytosis & activation of DCs
2.Activated DC migrate to secondary lymphoid organ (lymph node)
3.Mature DC try to activate specific naive T cell
-3 signals:
Proliferation
Clonal expansion
differentiation
Other lymphoid organs in the body
Lymph nodes
Spleen
Peyer’s patch
Primary/central - generates
Secondary – activated
DCs enter lymph node via
afferent lymphatics
T & B cells enter via
HEV – High Endothelial Venules (blood circulation)
HEV are Post-caspillary venules found in lymph nodes
how does Transferring antigens to DCs work
Activated DCs loaded with Ag enter lymph node
-Thye can transfer antigen to resident DCs
when does Transferring antigens to DCs happen?
-Happens if antigens from viruses rapidly kill the dendritic cells
-If cDC absent – tissue-resident macrophages with DC morphology (LCs)
(Responsible for initial uptake & transport & then transfer the antigen )
Lymphocytes constantly
travelling
Naive lymphocytes are constantly
scanning for their specific Ag that they can respond to
-Spend hours in secondary lymphoid organs
what happen if naive lymphocyte find no match
they exit & return to blood & restart the search in another lymph node
If T cells don’t encounter Ag –> leaves via
efferent lymphatics
when would T cell stay in lymph node?
T cell that has encountered its specific Ag presented by DC
what happens to T cell in lymph node
T cell is activated, proliferates & differentiates
Effector T cells exit lymph node via & what ehlps them to lead to site of infection?
efferent lymphatics & home to infected tissue
Chemokine receptors & adhesion molecules
Lead to site of infection
