t chapters of the book go into an in-depth description of the immune system. It tells exactly how the T and B cells are created and the complexity of their individual jobs. It describes bodies called Macrophages that engulf foreign bodies and chop them up to warn the body of potential danger. The body's immune system works well against viral and bacterial invaders but it is useless against parasites. They have their own cache of immune suppressing drugs that they pump into the body to fool it, change their coats or genetic make-up and some even use parts of their host's body to disguise themselves. Some parasites, like Toxoplasma, actually stimulate the human immune system to keep itself in check, yet it does no harm to the human body. In many cases, it is not the parasite that kills it's host, for that would be at it's own disadvantage, but rather the host's immune system that goes out of control, eventually harming the body instead of the invader. The equilibrium between the amount that parasite takes from the body and the harm that taking from the body actually causes is called "virulence".
             Protozoa and single celled eukaryotes do not make up the entire parasite kingdom. In fac
             ...