The immune system attacks foreign cells - be they tumor cells, virally infected, or donated by another person - when T lymphocytes recognize antigenic peptides displayed on the cell surface.

• 当T淋巴细胞识别出细胞表面存在抗原多肽时，免疫系统便将其认为异种细胞，并开始攻击，这些异种细胞包括肿瘤细胞，病毒感染的细胞和来源于捐赠人的细胞。