inflammation

Chapter 6 Chronic inflammation




Questions


image What is chronic inflammation?

image How may chronic inflammation be manifest clinically?

image What are the major cells types involved in chronic inflammation and what are their roles?

Chronic inflammation is characterized by tissue damage and attempts at repair occurring simultaneously. It may follow acute inflammation, or it may occur ab initio without preceding acute inflammation. Examples of chronic inflammatory processes that develop without a preceding acute phase are:


image infection with organisms that are predominantly intracellular, e.g. tuberculosis, viruses

image presence of foreign body, e.g. suture materials, implanted prostheses, inhaled dusts

image many autoimmune diseases

image cellular rejection of transplants.

The inflammatory cells that characterize the chronic inflammatory response histologically are macrophages and their derivatives, lymphocytes, plasma cells and eosinophils. Pathologists refer to them as the ‘chronic inflammatory cells’. Unless present in the tissue already, these cells are recruited to the site of inflammation by a process similar to that described for neutrophils in Ch. 5. Vascular events are involved in chronic inflammation, similar to those that occur in acute inflammation.




The role of macrophages


In addition to their phagocytic function, macrophages have important coordinating roles in chronic inflammation by virtue of their interactions with other inflammatory cells, antigen presentation and secretion of cytokines. They are an important component of the adaptive immune response and act to orchestrate many of its functions. Unlike neutrophils, macrophages are long lived and can persist for a long time. Macrophages in inflamed tissues are derived from blood monocytes produced in the bone marrow and are, therefore, part of the mononuclear phagocyte system (reticuloendothelial system). This system consists of the derivatives of monocytes and includes (Fig. 3.6.1):


image macrophages recruited to inflamed tissues from the bloodstream

image the fixed tissue macrophages such Kupffer cells in the liver, microglial cells in the brain and alveolar macrophages in the lungs

image specialized derivatives of macrophages such as epithelioid cells and multinucleate giant cells
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Jul 3, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on inflammation

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