Subject: Natural killer cells and red blood cells

Hi there,
I cannot access the "Ask and immunologist" site.  

I teach immunology to 2nd year Med Students.  We have just covered NK
cells and have discussed recent insights into their mechanism of
action.  Numerous students (and post-docs) would like to know why
erythrocytes, which do not express the MHC class 1 molecule, are not
killed by Nk cells.

Can you help me direct this question to someone who can throw some 
light
on this subject?

Many thanks

Re: Natural killer cells and red blood cells