ABSTRACT
An effective immune response coordinates the action of organs, circulating cells, and soluble components as an integrated system to eradicate foreign material encountered within the body. Many of these agents are already present within the circulation, under tight regulation yet able to migrate to the source of infection to mount a rapid response upon challenge. Others are stationed within lymphoid organs, awaiting stimulation to direct a targeted immune response. This chapter aims to provide a general overview of how our immune system develops, encompassing innate and adaptive (or acquired) aspects of immunity, their complex interactions, and the regulatory mechanisms that control their actions.
