Inflammation (Latin: inflammatio) is the body’s response to injury or infection. It is a protective mechanism that involves immune cells, blood vessels, and molecular mediators. The purpose of inflammation is to eliminate the initial cause of cell injury and to remove damaged cells and debris so that healing can take place.
Acute inflammation is a short-term process that occurs in response to tissue damage. It begins within minutes or hours of injury and resolves within days or weeks. Chronic inflammation is a long-term process that occurs in response to infectious agents or other irritants. It can last for months or years, and may result in permanent tissue damage.
The inflammatory response is initiated by the release of cytokines and other chemical signals from injured cells. These signals trigger the recruitment of immune cells to the site of injury. Immune cells secrete additional cytokines and other mediators that promote vasodilation, increased vascular permeability, smooth muscle contraction, and leukocyte migration into tissues.
Vasodilation increases blood flow to the area of injury, which brings more oxygen and nutrients needed for repair. Increased vascular permeability allows fluids and proteins to leak out of blood vessels into tissues, where they can help fight infection or repair damaged tissue. Smooth muscle contraction constricts blood vessels and decreases blood flow to the area of injury, which reduces swelling. Leukocyte migration helps rid tissues of bacteria and other foreign invaders through phagocytosis (engulfing and destroying them).
The inflammatory response is regulated by negative feedback mechanisms that prevent excessive tissue damage while still allowing for adequate healing. When these mechanisms fail, chronic inflammation can occur, which can lead to autoimmune disease, cancer, or other problems.