Dendritic cells process antigens from a wide array of pathogens Flashcards
Page 334-336 Chapter 8 T cell mediated immunity Janeway
From what types of pathogen can dendritic cells present antigen?
Virtually any type, due to having various mechanisms for taking up extracellular material
List two DC phagocytic receptors and what they recognise
- Mannose receptor
- DEC 205
These receptors recognise a wide array of bacteria and viruses
Antigens phagocytosed via the mannose or DEC 205 enter which processing pathway?
The endocytic processing pathway
How may microbes that have evolved to escape recognition by phagocytic receptors still be taken up by tissue DCs? What pathway do they enter?
Macropinocytosis -> and enter the endocytic processing pathway from there.
Dendritic cells are particularly important for stimulating T cell responses to viruses. Why? How are viruses taken up?
DCs are important for stimulating T cell responses to viruses because viruses can fail to stimulate co-stimulatory activity in other APCS.
Viruses are usually taken up via direct entry into the cytosol.
How do viruses synthesise their proteins in a DC? What then occurs to synthesised viral proteins?
They use the DCs cell-protein synthesis mechanisms, leading to proteasomal processing of viral proteins and surface presentation of viral peptidesbound to MHC class I molecules (as with any VIC).
Virus infected cells are recognised by which effector cell type?
CD8 effector T cells = cytotoxic T cells.
Cross presentation of viral particles on MHC I occurs when viral particles are taken up via what routes?
Phagocytosis or macropinocytosis
What does cross presentation of viral particles enable?
Cross presentation of viral particles that are not able to infect DCs ensures that these viruses are still able to stimulate effective antiviral responses by CD8 T cells.
What is the dual purpose of viral particles being presented on MHC II molecules?
These particles
- Activate naive CD4 T cells to become effector CD4 T cells that can stimulate antibody production by B cells.
- Cause CD4 effector T cells to secrete cytokines that enhance the immune response.
In infections with herpes simplex or influenza virus, what is the dominant DC responsible for priming naive CD8 T cells to become effector CD8 T cells?
A CD8 positive subset of DCs resident in the lymph node
Describe the 5 key steps from infection with herpes simplex to priming of naive CD8 T cells.
- Herpes simplex infection
- Viral particles taken up by tissue resident DCs (Langerhans cells)
- Tissue resident DCs travel to PLOs
- Tissue resident DCs transfer antigen to CD8 positive subset of DCs resident in PLOs
- This CD8 positive subset activates naive CD8 T cells
How does transfer of antigen to a CD8 positive DC in the PLO facilitate a prompt response to viral infection?
Antigens from viruses that infect but rapidly kill DCs can still be presented by uninfected DCs that take up antigen by cross-presentation and have been activated via their TLRs and chemokines.
Which cell cell type are Langerhans cells a typical example?
Immature conventional dendritic cells.
What are Birbeck granules and in which cell type are they found?
Birbeck granules are an endosomal recycling compartment found in Langerhans cells
