Expert: Florence M Rollwagen - 1/29/2009

Question
Do Antigen presenting cells (APC)have constitutively expressed MHCI and MHCII molecules on their surface at varying degrees before encountering the antigen? Why do they have MHCI. To what and how do the MHCI mols of the antigen presenting cells respond. What is the role of MHCI on the APCs? thankyou

Answer
Hi Shravani:  Thanks for your question (s)

The MHC cell surface molecules function to alert the immune system to exogenous and endogenous foreign proteins.

1.  Do Antigen presenting cells (APC) have constitutively expressed MHCI and MHCII molecules on their surface at varying degrees before encountering the antigen?
Ans:  Yes, and the relative densities control how or if the T cell can respond to Ag+MHC.  Ref: http://www.ncbi.nlm.nih.gov/pubmed/15081535?ordinalpos=11&itool=EntrezSystem2.PE...

http://www.ncbi.nlm.nih.gov/pubmed/12538693?ordinalpos=12&itool=EntrezSystem2.PE...

2 and 3.  Why do they have MHCI.
Ans:  All nucleated cells have Class I MHC.  They function to present endogenous antigens to the immune system, as opposed to Class II MHC which present exogenous antigens.  The Class I peptides function as “self non-self” antigens and to present endogenous virus peptides to the immune system.
Ref: http://en.wikipedia.org/wiki/MHC_class_I


Hope this helps!

FM Rollwagen, PhD