Humans or animals must defend themselves against multitude of different pathogens including viruses, bacteria, fungi, protozoan and metazoan parasites as well as tumors and a number of various harmful agents that are capable of deranging their homeostasis, resulting in infection and injury.
Inflammation is a complex defense mechanism that evolved in higher organisms to protect them from infection and injury. The term inflammation is derived from the Latin word “inflamatio” means “to set on fire” to signify heat associated with inflammation.
The complex stereotypical reaction of the body is a protective attempt to remove the injurious stimuli, damaged tissue components and also to initiate healing process of the damaged cells and vascularized tissues.
In vascular tissues such as cornea of eye, the true inflammation does not occur. The inflammatory reaction is the oldest defense mechanism both phylogenetically and ontogenetically.
In the absence of inflammation, wounds and infections would never heal and progressive destruction of the tissue would compromise the survival of the organism.
Since the cells of the immune system are widely distributed throughout the body, inflammation concentrates them and their products at the site of damage, to remove damaged tissue components and to initiate healing process.
The five basic symptoms of inflammation – redness (rubor), swelling (tumour), heat (calor), pain (dolor) and deranged function (functio laesa) have been known since long time.
The first four classical signs were described by Celsus (ca 30 BC-38 AD), while loss of function was added later by Virchow in the year 1870. Early investigators considered inflammation a primary host defense system.
But inappropriate activation of inflammatory responses is the underlying cause of many common diseases such as arthritis and gout. Some times it can lead to death also, as in anaphylactic shock.