Mediators

Mediators are defined as communication molecules derived from one cell type that act on another by virtue of specific receptors, and are intermediate in lifespan between the long-lived hormones and the short-lived and local acting neuro-transmitters. These mediators are released by all blood and stromal cells of the haemopoietic and lymphoreticular systems, particularly macrophages, lymphocytes, endothelial cells and fibroblasts. Little is known about normal control mechanisms because under steady-state conditions mediators are released locally and act locally. Only when produced in excess are they detectable in the bloodstream. The terminology of mediators is confusing and the terms mediator, cytokine, growth factor, monokine, lymphokine and IL are often used interchangeably. In this chapter the term mediator will be used as the all-inclusive term for cellular

Signal transduction

Resting (Unassembled oxidase)

Signal transduction

Resting (Unassembled oxidase)

Cytokine

Cytokine

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