The immune system hunts "foreign proteins". That is, the immune system
has tolerance for proteins it has seen in your body, and attacks any cell
making anything else. This is why it's very difficult to find transplant
donors, as your immune system will recognize that an organ coming from
someone else has proteins that didn't come from you. Here, the immune
system presumes that unusual proteins probably came from a virus, and in
this case it happens to be right. Unfortunately, the immune system may,
in response, kill off the very cells we just finished curing.
Slide 14