What is the difference between the innate and adaptive immune systems?

The immune system can be divided into innate and adaptive components.1 The innate immune system activates upon first contact with a pathogen, eliciting a broad and largely non-targeted response characterized by inflammation and phagocytosis. The innate immune system response also serves to prime the adaptive immune system by sequestering and presenting pathogen antigen, facilitating the maturation and activation of adaptive immune cells.

After a short span (usually several days), the innate immune system self-downregulates and the adaptive immune system becomes more active.1 The adaptive immune response is highly selective, targeting only entities expressing the same antigen presented to the adaptive immune cells during maturation and activation. The adaptive immune system also facilitates immunity, as subpopulations of “memory” effector cells remain after the immune response has ceased, resulting in a faster response upon a second contact with the antigen. For related information on immunotherapy please visit our resource center.

1. C.A. Janeway Jr., et al., Immunobiology: The Immune System in Health and Disease. 6th edition. New York: Garland Science; 2005.