How do the different parts of the immune system work?

The human body is a perfect machine that always faces constant enemies like the cold, the viruses, the bacteria or the microbes that coexist with us trying. The human body is a perfect machine that always faces constant enemies like the cold, the viruses, the bacteria or the microbes that coexist with us trying. The human body is a perfect machine that always faces constant enemies like the cold, the viruses, the bacteria or the microbes that coexist with us trying.