________ cells can lyse and kill cancer cells and virus-infected body cells before the immune system is activa?

Natural killer cells (or NK cells)

They are a type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virally infected cells and respond to tumor formation, acting at around 3 days after infection.

Natural killer cells. Cytotoxic T cells are similar cells, but they are part of the adaptive immune response.

http://en.wikipedia.org/wiki/Natural_killer_cell

Best wishes and good luck.

i would say cytotoxic T cell...but i'm not totally positive...the "before the immune system is activated is throwing me off a little

i'm continually optomistic yet on the comparable time careful because of the fact there have been many fake starts off and a few sturdy concepts seem to have been sabotaged on the way. i'm hoping that if this is on the wonderful song that it is going to likely be stepped forward to fulfilment. I pray to God that people who desperately are in seek of treatments would discover them.