The notion is, if there's something foreign that's being produced inside this cell, then that cell must have been corrupted in some way and it has to be gotten rid of.

免疫反应的规矩是这样的,如果某些外源物在你细胞内产生,那说明这个细胞的某些地方,已经被损害了所以必须被清除掉

耶鲁公开课 - 生物医学工程探索课程节选