They only kill cells that have the signal which stimulated them.

只能杀死那些带有能激活,它们的标记信号的细胞

耶鲁公开课 - 生物医学工程探索课程节选

Here's where the intelligence of the immune system comes in, is that these cytotoxic T-cells that are generated only kill cells that have this signal on it.

免疫系统的聪明之处就在此,这些细胞毒T细胞,只能杀死具有特殊标记信号的细胞

耶鲁公开课 - 生物医学工程探索课程节选