The Immune System
The human immune system is a network of cells and proteins that interact to protect against foreign challenges. This complex system is subdivided into innate and adaptive immune systems. The innate immune system is the first line of defense against pathogens and is characterized as “non-specific” because it functions against pathogens in general. Adaptive immunity is initiated following the activation of the innate system and is characterized as “specific,” because it generates long lasting immunological memory to specific antigens within the foreign pathogens or on their surface. There are hundreds of different types of receptors on the surface of immune cells that control and activate the complex cellular and molecular interactions between these two subsystems. In real-life, these two arms work in concert to protect the body from health challenges.
The innate immune system is composed of billions of white blood cells that are the body’s first line of defense. These cells, which can distinguish between self and non-self, patrol the body in search of foreign pathogens. Once such organisms are detected, cells of the innate immune system respond rapidly (in minutes or hours) with a number of non-specific killing mechanisms designed to destroy the intruding organisms. Innate immune cells also play an important role in initiating the adaptive immune response which is slower (in days or weeks) yet generates a specific killing mechanism targeting a particular intruding organism, such as a specific bacteria or virus.