Chronic Inflammation Develops When Antigen Persists

Some microorganisms are able to evade clearance by the immune system, for example by possessing cell-wall components that enable them to resist phagocytosis. Such organisms often induce a chronic inflammatory response, resulting in significant tissue damage. Chronic inflammation also occurs in a number of autoimmune diseases in which self-antigens continually activate T cells. Finally, chronic inflammation also contributes to the tissue damage and wasting associated with many types of cancer.

The accumulation and activation of macrophages is the hallmark of chronic inflammation. Cytokines released by the

VISUALIZING CONCEPTS

VISUALIZING CONCEPTS

Hypothalamus

(via pituitary)

Prostaglandins

Fever

(via pituitary)

Adrenal cortex

Local acute inflammatory response

Hypothalamus

Prostaglandins

Adrenal cortex

Chronic Inflammation Damage

Liver

Bone marrow ( f CSF by stromal cells and macrophages)

Liver

Acute-phase proteins: C-reactive protein (CRP) Serum amyloid A (SAA) Fibrinogen

Mannose-binding protein Complement components

Bone marrow ( f CSF by stromal cells and macrophages)

Leukocytosis ( X white blood cells)

FIGURE 15-13

Overview of the organs and mediators involved in a systemic acute-phase response. IL-1, IL-6, and TNF-a, which are produced by activated macrophages at the site of inflamma tion, are particularly important in mediating acute-phase effects. LIF = leukemia inhibitory factor; OSM = oncostatin M.

chronically activated macrophages also stimulate fibroblast proliferation and collagen production. A type of scar tissue develops at sites of chronic inflammation by a process called fibrosis, a wound-healing reaction that can interfere with normal tissue function. Chronic inflammation may also lead to formation of a granuloma, a tumor-like mass consisting of a central area of activated macrophages surrounded by activated lymphocytes. The center of the granuloma often contains multinucleated giant cells formed by the fusion of activated macrophages. These giant cells typically are surrounded by large modified macrophages that resemble epithelial cells and therefore are called epithelioid cells.

How To Reduce Acne Scarring

How To Reduce Acne Scarring

Acne is a name that is famous in its own right, but for all of the wrong reasons. Most teenagers know, and dread, the very word, as it so prevalently wrecks havoc on their faces throughout their adolescent years.

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