Biological mediators of acute inflammation.

Inflammation may be defined as the normal response of living tissue to injury or infection. It is important to emphasize two components of this definition. First, that inflammation is a normal response and, as such, is expected to occur when tissue is damaged. Indeed, if injured tissue did not exhibit signs of inflammation this would be considered abnormal. Secondly, inflammation occurs in living tissue, hence the need for an adequate blood supply to the tissues in order for an inflammatory response to be exhibited. The inflammatory response may be triggered by mechanical injury, chemical toxins, invasion by microorganisms, and hypersensitivity reactions. Three major events occur during the inflammatory response: the blood supply to the affected area is increased substantially, capillary permeability is increased, and leucocytes migrate from the capillary vessels into the surrounding interstitial spaces to the site of inflammation or injury. The inflammatory response represents a complex biological and biochemical process involving cells of the immune system and a plethora of biological mediators. Cell-to-cell communication molecules known collectively as cytokines play an extremely important role in mediating the process of inflammation. An extensive exposition of this complex phenomenon is beyond the scope of this article. Rather, the author provides a review of inflammation, an overview of the role of certain biological mediators in inflammation, and a discussion of the implications of certain biological response modifiers in clinical practice.