Antigen Presentation and the MHC Flashcards
What is on the surface of professional antigen presenting cells?
Both Class I and Class II MHCs
Of the APCs which one is not phagocytic?
B lymphocytes
How do dendritic cells change in function as they mature?
Immature DCs are phagocytic, mature ones are not.
What are plasmacytoid dendritic cells?
Plasmacytoid dendritic cells produce large quantities of interferon in response to viral infections.
What are conventional dendritic cells?
They develop from highly phagocytic cells to mature dendritic cells that present large quantities of peptide in the context of MHC class II molecules.
What is the difference in the antigen presentation of B lymphocytes VS DCs?
B lymphocytes present only one kind of antigen via cell surface receptor
Describe antigen processing in Class I MHC.
Viral proteins in the cytoplasm are bound by MHC Class I proteins and are transported to the cell surface for antigen presentation.
Describe antigen processing in Class II MHC.
Extracellular protein is taken into vesicles into the cell and the vessel is acidified and proteases are active to break them down and MHC Class II vesicles fuse and bind the peptides. It is then exported to the cell membrane.
Describe Class II MHC antigen processing on B lymphocytes.
Antigen specific B cell binds its antigen and it is taken in and vesicles of the MHC Class II receptor join it and the antigen is bound and exported to the membrane.
For antigen processing in Class I, what degrades the antigens?
Proteasome
Where are the degraded Class I MHC antigens taken to and how?
They are transported to the endoplasmic reticulum of the cell by TAP1 and TAP2 transporters.
What are the chaperones that help the MHC Class I proteins fold?
Calnexin/Calreticulin/ERp57
What is the function of ERAAP?
When peptides are transported into the endplasmic reticulum they are trimmed by ERAAP before binding to the MHC
What do Class I MHCs present under normal conditions?
Present normal host peptides
How is the Class II MHC receptor prepared for binding antigens? (Involves invariant chain and CLIP)
Within the endosome, acidification cleaves Invariant Chain leaving a short peptide fragment, CLIP. CLIP is removed by HLA-DM and foreign antigen is loaded.
