The purpose of the immune system is to keep infectious microorganisms, such as certain bacteria, viruses, and fungi, out of the body, and to destroy any infectious microorganisms that do invade the body. The immune system is made up of a complex and vital network of cells and organs that protect the body from infection.

    

Immune system is the protective power of the body which protects it from various kind of infections.
Actually,we have ''white Blood Cells''in our body which act as immune system and keep it fit.Some W.B.Cs are specific for specific infections which produce special type of immunoglobulin protein for that particular type of infection.