Flashcards in Lecture 14 - Antigen-Presenting Cells Deck (33)
What do T cells do in a naive state?
Circulate between lymphoid organs and tissues in lymph.
Can't elicit effector function
Time taken for a naive T cell to mature
Where do most pathogens reside?
What is an APC versus a professional APC?
APC is any cell with MHCI
Professional APC is a cell with MHCII (EG: dendritic cell)
Dendritic cell life
1) Grows in the bone marrow
2) Travels to tissue
3) Stays in tissue for several days, picks up antigens
4) Takes antigens to lymph node, presents them, dies
Dendritic cells in epidermis
How do dendritic cells enter a lymph node?
Through the afferent lymphatics
Types of dendritic cells
1) a, b
1) Conventional dendritic cell
2) Inflammatory dendritic cell
3) Plasmacytoid dendritic cell
Why doesn't the spleen receive dendritic cells?
The spleen receives no lymph
What do CD8+ conventional dendritic cells arise from?
CD24high progenitors in the spleen
What do CD8- conventional dendritic cells arise from?
CD24low progenitors in the spleen
Best at presenting on MHCII
Best DC at presenting on MHCII
Types of conventional DCs (apart from CD8+/-)
1) Peripheral tissue-resident --> present in most peripheral tissues, but different tissues have different DC types.
2) Lymphoid-tissue resident --> Two types - CD11blo, CD11bhigh
1) Non-existent in healthy state
2) Differentiate from monocytes under inflammatory conditions
3) Antigen presentation to tissue effector cells
Why are inflammatory DCs important in inflamed tissue?
Tissue CD4 T cells need MHCII presentation
iDCs do this
1) When inactive, look like plasma cells
2) When activated, look like dendritic cells
3) Good at secreting IFN1, IFN2
4) In blood and tissues
1) DCs circulate in immature state, with high phagocytic activity and poor antigen-presenting capacity
2) When a PRR is stimulated, DC matures, begins antigen presenting
Way for DCs to recognise intracellular bacteria
Why don't dendritic cells activate T cells against self antigens?
If a DC begins presenting a self antigen but there are no PAMPS, it will not mature, and therefore not be able to stimulate T cells with self antigen
How does a DC encounter a virus?
Very rare to encounter virus in extracellular fluid
Phagocytoses a dead cell, viral antigens are detected by TLRs in endosome
Most important antiviral cytokines
IFN type I, II
TLR9 stimulation effect
1) IL12 (Th1)
2) CD40 (B cell activation)
3) CD80, 86 expression (T cell activation)
RIG-like helicase ligand
RIG-like helicase receptor
RIG-like helicase location
RIG-like helicase stimulation effect
IFNa, b expression