I was studying immunology and came across the natural killer cell. From my understanding, natural killer cells basically kill cells that lack MHC I (found on all nucleated cells and platelets). I guess my question is then why don't natural killer cells kill our own RBCs? What is the marker/surface antigen that prevents RBC destruction?
In addition, I understand that the testes are an immunologically privileged area of the body; however, when sperm enter the female vaginal tract, why aren't natural killer cells activated by the lack of MHC on sperm?
Hope these aren't stupid questions.....maybe I overlooked something totally obvious.