Why will MHC indicate graft as foreign?

Hobo noemail at noemail.com
Tue Jul 8 17:59:41 EST 2003

In article <beeaks$bof$1 at reader1.panix.com>,
 iayork at panix.com (Ian A. York) wrote:

> Cancer cells probably don't express MHC homologues.  However, your general 
> point may be right, because it's possible that some viruses that 
> downregulate MHC class I do express MHC class I homologues (e.g. 
> cytomegalovirus).  The function and mechanism of these homologues isn't 
> quite clear, and that's true for viral immune evasion in general.  Viruses 
> (as opposed to cancer cells) *may* only have to delay recognition and 
> killing, rather than avoid it forever, so that the virus can complete 

Why don't NK cells kill red blood cells, which don't express MHC Class 
Ones, and why don't red blood cells express MHC Class Ones? Is it 
because without a nucleus MHCs are not needed, or is because without a 
nucleus they can not be produced?

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