Immunology is the science that is concerned with immune response to foreign challenges. Immunity
(derived from Latin term immunis, meaning exempt), is the ability of an organism to resist infections
by pathogens or state of protection against foreign organisms or substances. The array of cells,
tissues and organs which carry out this activity constitute the immune system.
The immune system is remarkably versatile defence system that has evolved to protect animals from
invading pathogenic microorganisms and cancer. It is able to generate an enormous variety of cells