21. Antigen Capture and Presenation

Question 1

A 45 year old women has had persistent viral infection. She goes to the hospital and it is found that the while there are viral peptides in the cytosol they fail to make it into the ER. What is the cause of this problem?

A.  Malfunctioning Proteasome 
B. Adenoviral Protein
C. HSV Protien
D.  Overactive HLA-DO 
E. Malfunctioning Endosome

RFA

Answer 1

ANS C- HSV Protein- blocks the TAP preventing viral peptides being brought into the ER and attaching to MHCI

A. Malfunctioning Proteasome- since the Viral Protein is present as viral peptides in the cytosol it is working

B. Adenoviral Protein- Prohibits MCHI from leaving the ER and being presented on the cell surface instead having it being destroyed by lysosomes

D. Overactive HLA-DO- HLA-DO inhibits HLA-DM, which removes the CLIP from MHCII but since this is a viral infection and MHC II is more bacterial exogenous antigens it is not the best answer

E. Malfunctioning Endosome- since there is peptides in the cytosol this should be eliminated from consideration also the Endosome is in the MHCII pathways and this more like MHCI related

Question 2

Which of these are true of MHCI?

A. Presents exogenous antigens 
B.  Bind peptides 8-10 AA
C.Binds peptides 13-25 AA
D. Has a Transmembrane beta chain
E. Expressed on only APC

RFA

Answer 2

ANS. B. MHCI -8-10 AA binding

A. Exogenous antigens- MCHII

B. 13-25- AA MHCII

D. Transmembrane beta chain- has a transmembrane alpha chain and Beta-2 microglobulin, MHCII trans membrane Alpha and beta chains

E. Only APCs- MHCII is only APC, MHCI is all nucleated cells.