Immunology is the branch of biomedical science that deals with the response of an organism to antigenic challenge and its recognition of what is self and what is not. It deals with the defence mechanisms including all physical, chemical and biological properties of the organism that help it to combat its susceptibility to foreign organisms, material, etc.
The immune system is a complex system of structures and processes that has evolved to protect us from disease. Molecular and cellular components make up the immune system. The function of these components is divided up into nonspecific mechanisms, those which are innate to an organism, and responsive responses, which are adaptive to specific pathogens. Fundamental or classical immunology involves studying the components that make up the innate and adaptive immune system.