They are called natural killer cells, and you can think of natural killer cells almost like the secret service agents of your immune system.

它们被称为自然杀伤细胞，您可以将自然杀伤细胞视为免疫系统的特工。

But perhaps the scariest fact is that even after one night of 4-5 hrs of sleep, your natural killer cells, which stop cancer cells from proliferating in your body drop by 70%.

但也许最可怕的事实是，即使只睡4-5个小时，你体内阻止癌细胞增殖的自然杀伤细胞也会减少70%。