body fighting transplants (hey, that's close to being a contronym, how awesome is that)

Just to complete the set, there's also the inverse: the transplant fighting the host ("graft-versus-host"). Imagine how confused you'd feel as a sentient leukocyte, grafted onto a different body.

ヽ༼ຈل͜ຈ༽ﾉ Transplant hwaiting! ヽ༼ຈل͜ຈ༽ﾉ