INFLAMMATION COURSE CODE : PHR 214 COURSE TEACHER : ZARA SHEIKH

Inflammation Damage to the body's tissues triggers a local defensive response called inflammation, another component of the second line of defense. The damage can be caused by microbial infection, physical agents (such as heat, radiant energy, electricity, or sharp objects), or chemical agents (acids, bases, and gases). Inflammation is usually characterized by four signs and symptoms: redness, pain, heat, and swelling. Sometimes a fifth, loss of function, is present; its occurrence depends on the site and extent of damage.

Inflammation If the cause of an inflammation is removed in a relatively short period of time, the inflammatory response is intense and is referred to as an acute inflammation. An example is the response to a boil caused by S.aureus. If, instead, the cause of an inflammation is difficult or impossible to remove, the inflammatory response is longer lasting but less intense (although overall more destructive). This type of inflammation is referred to as a chronic inflammation. An example is the response to a chronic infection such as tuberculosis, caused by M. tuberculosis.

Inflammation Inflammation has the following functions: (1) to destroy the injurious agent, if possible, and to remove it and its by-products from the body (2) if destruction is not possible, to limit the effects on the body by confining or walling off the injurious agent and its by-products. (3) to repair or replace tissue damaged by the injurious agent or its by-products.

Inflammation Q. What are acute-phase proteins? During the early stages of inflammation, microbial structures, such as flagellin, lipopolysaccharides (LPS), and bacterial DNA stimulate the Toll-like receptors of macrophages to produce cytokines, such as tumor necrosis factor alpha (TNF-α). In response to TNF- α in the blood, the liver synthesizes a group of proteins called acute-phase proteins; other acute-phase proteins are present in the blood in an inactive form and are converted to an active form during inflammation..

Inflammation Acute-phase proteins induce both local and systemic responses and include proteins such as C- reactive protein, mannose-binding lectin and several specialized proteins such as fibrinogen for blood clotting and kinins for vasodilation. Stages of inflammation : The process of inflammation into three stages: vasodilation and increased permeability of blood vessels, phagocyte migration and phagocytosis, and tissue repair.

Inflammation 1. Vasodilation and Increased Permeability of Blood Vessels Immediately following tissue damage, blood vessels dilate (increase in diameter) in the area of damage, and their permeability increases. Dilation of blood vessels, called vasodilation, increases blood flow to the damaged area and is responsible for the redness (erythema) and heat associated with inflammation.

Inflammation Increased permeability permits defensive substances normally retained in the blood to pass through the walls of the blood vessels and enter the injured area. The increase in permeability, which permits fluid to move from the blood into tissue spaces, is responsible for the edema (accumulation of fluid) of inflammation. The pain of inflammation can be caused by nerve damage, irritation by toxins, or the pressure of edema.

Inflammation Vasodilation and the increase in permeability of blood vessels arc caused by a number of chemicals released by damaged cells in response to injury. One such substance is histamine, a chemical present in many cells of the body, especially in mast cells in connective tissue, circulating basophils, and blood platelets. Histamine is released in direct response to the injury of cells that contain it; it is also released in response to stimulation by certain components of the complement system

Inflammation Phagocytic granulocytes attracted to the site of injury can also produce chemicals that cause the release of histamine. Kinins are another group of substances that causes vasodilation and the increase in permeability of blood vessels. Kinins are present in blood plasma and once activated, they play an important role in chemotaxis by attracting phagocytic granulocytes, chiefly neutrophils to the injured area.

Inflammation

repair. However, if repair cells of the stroma of the skin arc more active, scar tissue is formed. Q. What is fibrosis? Ans : Some microbes have various mechanisms that enable them to evade phagocytosis. Such microbes often induce a chronic inflammatory response, which can result in significant damage to body tissues.

Inflammation The most significant feature of chronic inflammation is the accumulation and activation of macrophages in the infected area. Cytokines released by activated macrophages induce fibroblasts in the tissue stroma to synthesize collagen fibers. These fibers aggregate to form scar tissue, a process called fibrosis. Because scar tissue is not specialized to perform the functions of the previously healthy tissue, fibrosis can interfere with the normal function of the tissue.

Topics done in class Distinguish between acute and chronic inflammation What are cytokines? Role of cytokines in chronic inflammation Chronic inflammatory diseases -Asthma -Chronic periodontis -Rheumatoid arthritis -Tuberculosis -Chronic active hepatitis

Topics done in class Definition of -Ulcer -Granulomatous inflammation -Granuloma

References: Microbiology : An Introduction by Tortora, Funke and Case Chapter -16 Kumar, Rakesh K, and Wakefield, Denis(Sep 2010) Inflammation: Chronic. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: / a pub3]