What is inflammation?

Inflammation as mediated by various cooperating components of the immune system is basically a protective and reparative response to tissue injury. In certain clinical situations, however, inflammation itself may be the cause of tissue destruction. The factors responsible for specifying or selecting the area in which inflammation will occur are still speculative. Of central importance in inflammatory reactions is the blood vessel system, which serves as a transport system for inflammation-initiating and perpetuating factors and which is itself involved in systemic or organ-specific tissue-destructive reactivities. The histopathological substrate of inflammation is tissue infiltration with mononuclear cells. Utilizing monoclonal reagents, it has become possible not only to separate different lymphocyte subpopulations and cells of the monocyte/macrophage lineage but also to identify mediators such as different interleukins and interferons which play a major part in acute and chronic inflammatory mechanisms.