Our immune system is a complex system of structures and processes that has evolved to protect us from disease. It is made up of molecular and cellular components, which functions can differentiated as nonspecific mechanisms, those which are innate to an organism, and responsive reactions which are adaptive to specific pathogens. 

The immune system is made up of many types of molecules and cells that are distributed in every tissue of the body, as well as specialised lymphoid organs. This system works to prevent or eliminate microbial infections, impact the growth of tumours, and repair damaged tissues. 

The immune system normally recognises and responds to foreign molecules or damaged self, but not healthy host cells and tissues.