Now, if the U.S. has any hard evidence like blood, tissue, soil samples, it isn't saying.

美国并没有说明是否掌握了血液、组织、土壤样本等铁证。

As they move around, leukocytes work like security personnel, constantly screening the blood, tissues, and organs for suspicious signs.

当它们四处移动时， 白细胞就像安保人员一样工作，不断检查血液、组织和器官是否有可疑迹象。