Common Science

I was recently asked about the surveillance system present within immunity which operates to kill virally infected cells by lack of MHC expression, and why this same system doesn't destroy red blood cells (RBC), which lack MHC. One function of Natural Killer (NK) cells is to destroy cells infected by viruses, which have a mechanism of evading T-cell killing by down-regulating MHC class I expression. MHC class I molecules are expressed on every cell in the body apart from RBCs; a lack of expression is detected by NK cells which act to destroy the cell. However, RBC remain unharmed. SEM of NK cells Red Blood Cells                         V.S Like everyone else I assumed the almighty google would provide me with the answer to my friends question, so I typed in my query and the only relevant link was to a 'yahoo answers' page, which answered a succinctly phrased question which I've used to entitle this blog entry. Unfortunately the answer just stated