Inflammation PDF

Inflammation 1. Classification 2. Cardinal signs 3. Nomenclature Inflammation is a defensive host response to foreign invaders and necrotic tissue The main components of inflammation:  Vascular reaction and a cellular response  both are activated by mediators derived from plasma proteins and...

Inflammation 1. Classification 2. Cardinal signs 3. Nomenclature Inflammation is a defensive host response to foreign invaders and necrotic tissue The main components of inflammation:  Vascular reaction and a cellular response  both are activated by mediators derived from plasma proteins and various cells  Inflammation accomplishes its protective mission by first diluting, destroying, or neutralizing harmful agents (microbes, toxins)  The inflammatory reaction and the subsequent repair process can themselves cause considerable harm The goal of the inflammatory reaction is to bring cells and molecules of host defense to the site of infection or tissue damage The steps of the inflammatory response (the five Rs):  Recognition of the injurious agent  Recruitment of leukocytes  Removal of the agent  Regulation (control) of the response  Resolution (repair)  The outcome of acute inflammation is either elimination of the noxious stimulus, followed by repair of the damaged tissue, or persistent injury resulting in chronic inflammation  Acute Inflammation  Is rapid in onset and of short duration and is characterized by fluid and plasma protein exudation and a predominantly neutrophilic leukocyte accumulation Two major components: 1. Vascular changes:  Vasodilation: Alterations in vessel caliber resulting in increased blood flow  Increased vascular permeability: Changes in the vessel wall that permit plasma proteins to leave the circulation 2. Cellular events:  Cellular recruitment: Emigration of the leukocytes from the circulation and accumulation in the focus of injury  Activation of the leukocytes: Enabling them to eliminate the offending agent  The principal leukocytes in acute inflammation are neutrophils (polymorphonuclear leukocytes)  Stimuli for Acute Inflammation Acute inflammatory reactions may be triggered by a variety of stimuli:  Infections (bacterial, viral, fungal, parasitic) are among the most common and medically important causes of inflammation  Trauma and various physical and chemical agents (thermal injury, such as burns; irradiation; toxicity)  Tissue necrosis (from any cause), including physical and chemical injury  Foreign bodies (splinters, dirt, sutures, crystal deposits)  Immune reactions (hypersensitivity reactions) against environmental substances or against “self” tissues  Cardinal Signs of Inflammation:  Redness: Caused by dilated blood vessels in the affected area  Heat: Caused by increased blood flow to the area, and only felt in peripheral areas like the skin  Swelling: Known as edema, is caused by fluid building up outside of blood vessels  Pain Caused by chemical mediators, and tissue distortion from edema  Loss of function: Might not be able to use normally the affected part of body  Chronic Inflammation Inflammation of prolonged duration (weeks to years) in which continuing inflammation, tissue injury, and healing, often by fibrosis, proceed simultaneously Chronic inflammation is characterized by:  Infiltration with mononuclear cells, including macrophages, lymphocytes, and plasma cells  Tissue destruction, largely induced by the products of the inflammatory cells  Repair, involving new vessel proliferation (angiogenesis) and fibrosis Chronic inflammation may arise in the following settings:  Persistent infections by microbes that are difficult to eradicate (Mycobacterium, Treponema pallidum, and certain viruses and fungi  Immune-mediated inflammatory diseases; chronic inflammatory diseases, (rheumatoid arthritis, inflammatory bowel disease, and psoriasis)  Prolonged exposure to potentially toxic agents Eg. nondegradable exogenous materials such as inhaled particulate silica  Mild forms of chronic inflammation may be important in the pathogenesis of many diseases that are not conventionally thought of as inflammatory disorders Granulomatous Inflammation  Granulomatous inflammation is a distinctive pattern of chronic inflammation characterized by aggregates of activated macrophages Granulomas can form under three settings:  With persistent T-cell responses to certain microbes Tuberculosis is the protoype of a granulomatous disease caused by infection  Granulomas may also develop in some immune- mediated inflammatory diseases, notably Crohn disease,  Granulomas are also seen in a disease of unknown etiology called sarcoidosis  They develop in response to relatively inert foreign bodies (suture or splinter), forming foreign body granulomas Foreign body giant cells