Ag Capture Flashcards
DEscribe plasmacytoid dcs
Innate immunity and induce T cell responses against viruses
What is the structure of HLA I?
HLA 1 has 1 chain. An alpha chain which forms three globular domains a1 a2 and a3. Peptide binds within a1 and a2. Associated with the alpha chain is B2 microglobulin it is NOT MHC encoded and associates non covalently with a3 for structural support.
The binding cleft between a1 and a2 has the most polymorphism it is also closed so only 8-10 aa can fit.
Describe the MHC II binding cleft
Formed by a1 and B1 open and can fit 13-18 aa
Describe DC’s.
High constitutive expression of HLA II and co stimulators molecules. Can activate naive mature T cells.
Present a processed Ag to circulating mature naive lymphocytes in peripheral lymphoid tissues.
What are the genes for MHC II?
Three sets of genes and two chains alpha and beta. Genes are HLA-DQ,Dr, and DP.
MHC II synthesis and assembly?
The protein Ags from microbe are being broke down within phagolysosomes. A and b chains are translated into the ER and chaperone proteins hold them in proximity to each other before interaction with invariant chain (CLIP). This gets transported into a late endosome where an HLA-DM is and it exchanges CLIP for the peptide Ag produced by the lysosomal enzymes. Then it is all exocytosed to the surface.
Which MHC class is more diverse and why?
Class 1 is more diverse than two. There are a larger amount of allotypes in type one. However, type two has a greater variability than class one as they respond to outside threats.
Describe the structure of MHC II.
Four domains not covalently bound, the peptide holds them together once it is in the groove between alpha 1 and beta 1. There are 6 alpha chains and 6 beta chains three from each parent and any alpha chain can pair with any beta chain.
What do DC’s express?
Lose CCR7 and increase CD80 (B7)
Travel to secondary lymphoid tissues and mature as they migrate
How is MHC I put together ?
Viral infected host cells are ubiquinated for destruction by proteasome. The peptides are sent through TAP and attached to Tapasin which exchanges and moves peptides from cytosol to ER where it can be loaded into MHC I. A chains are translated into the ER and held in place with a chaperone protein. B2 microglobin replaces chaperone when peptide fragments are added to a chain. From the ER it goes to Golgi and then to surface. Uses TAP and Tapasin.
What are the components of CLass II
TAP and HLA-DM
CD4 and also HLA-DR, DP,DQ
What are the three separate gene regions that encode HLA I?
A B and C. Expressed on ALL nucleated cells and discriminates self from non self. Presents to CD8
Engages CD99/NKG2A receptor to inhibit NK killing
Describe the MHC genes.
Located on chromosome #6 there are three classes of HLA
Where do Ag enter via periphery go to?
Filtered through lymph and lymphoid tissues
If in blood it is filtered by blood
