[thedoc (OP)]

Jonathan Michael Acha  asked the Naked Scientists:
     
Hi, I would like to ask, if Natural Killer cells attack cells that have insufficient MHC class I molecules in their surface, then why don't they attack Red Blood Cells which are non-nucleated and have no MHC I molecules?

What do you think?

[rami999]

by its reciptors they know the body reciptors so they attack any unfamilliar reciptor

[evan_au]

why don't (Natural Killer cells) attack Red Blood Cells which are non-nucleated and have no MHC I molecules?

Because they all attended Thymus Immune Cell High School, where they only graduate if they don't attack normal cell types found in the body.

See: https://en.wikipedia.org/wiki/T_cell#Positive_selection