Innate immunity

Abstract

Innate immunity. The immune system is widely dispersed throughout the body, but must act in a concerted fashion to exert effective responses to both self and foreign antigens. The immune system is so effective at elimination of microbes because its specialized cellular components provide both an immediate broad protection (innate immunity) as well as delayed, finely tuned (adaptive) responses. The dominant cellular constituents of innate immunity are phagocytes (neutrophils, macrophages and dendritic cells), all of which are able to sense and ingest foreign material and, subsequently, secrete cytokines and chemokines to recruit and activate other immune cells. In addition, cells such as mast cells, basophils, NK and NK T cells provide more specialized innate functions that act rapidly in response to microbial or virus infection. In contrast, T and B lymphocytes, cells of adaptive immunity, can be regarded as sharpshooters-they precisely target antigens in order to remove foreign invaders from the body. One other key difference is that, once recruited into the immune response, a subset of adaptive immune cells differentiate into memory cells and can survive for the lifetime of the host. Innate immune cells, on the other hand, typically have short survival times (days) and do not exhibit immunological memory.