人们一度认为,增强人体的自然免疫系统似乎是治疗癌症的最有希望的途径之一。这种免疫系统能判别出肿瘤细胞,假如能让这种系统增加活动,它就可以消灭肿瘤细胞,正如它消灭病菌或任何别的不受欢迎的“入侵者”一样。免疫学家曾经认为,对癌细胞的免疫反应其实就是对抗细菌或对抗异体器官移植的作用。直到最近,免疫学家才开始证实存在一种对抗肿瘤细胞的“天然杀伤者”,即所谓 People once thought that enhancing the body’s natural immune system seems to be one of the most promising ways to treat cancer. This kind of immune system can distinguish tumor cells. If it can make this system more active, it can eliminate tumor cells just as it destroys bacteria or any other unwelcome “invaders.” Immunologists used to think that the immune response to cancer cells is actually an effect against bacteria or against allogeneic organ transplantation. Until recently, immunologists began to confirm the existence of a “natural killer” against tumor cells.