Immunity The human body has a natural ability to fight off various germs and toxins capable of damaging various tissues and organs of the body. This is called immunity. This power is of two kinds: 1. Self-motivated ( innate immunity) The immune system that is naturally present in the body is self -motivated. For example, there is no such thing as fever in the rain. Again, eating open food does not always cause diarrhea. The body simply kills some germs. 2. Acquired immunity The immunity that is formed in the body after being infected by a germ is called acquired immunity. For example, we see that once the spring is over, there is usually no more spring, or once the plague is over, it is no more.