Inflammation: Chronic


Chronic inflammation may result from failure to eliminate an irritant that causes acute inflammation, from an autoimmune response to a self‐antigen, or may be caused by an innately chronic irritant of low intensity that persists. It is a biologically distinct pattern of response in tissues that is characterised by simultaneous inflammation and repair. Recruitment and activation of macrophages is typical of chronic inflammation and is often accompanied by recruitment of cell types participating in an immunological response, notably T lymphocytes. Significant destruction of tissue may occur. Repair, which involves induction of granulation tissue, may lead to subsequent scarring. The chronic inflammatory response is regulated by the coordinated action of various cytokines and growth factors. Many common and clinically important diseases result from chronic inflammation, and this process also contributes to other diseases which are not primarily identified as inflammatory.

Key Concepts

  • Chronic inflammation is a key process underlying many common and important diseases, as well as other disease states which are not obviously inflammatory.
  • Compared to acute inflammation, chronic inflammation is a biologically distinct pattern of response, characterised by simultaneous inflammation and repair.
  • Macrophages and their derivatives are key participants in a chronic inflammatory response.
  • The immune response contributes to the pathogenesis of many chronic inflammatory diseases.
  • Chronic inflammation is regulated by a complex interaction among cytokines that promote inflammatory cell recruitment/activation and growth factors that promote healing.

Keywords: immunology; diseases and disorders; macrophage; granuloma; cytokines; repair

Figure 1. (a) Diffuse pattern of chronic inflammation in the wall of a chronic abscess of bone, with numerous dilated blood vessels (bv) surrounded by a mixture of inflammatory cells including neutrophils, macrophages and lymphocytes. (b) Diffuse pattern of chronic inflammation in the synovial membrane in rheumatoid arthritis; large numbers of lymphocytes and plasma cells (recognisable by their abundant dark pink cytoplasm) are visible beneath the layer of synovial cells (sc).
Figure 2. (a) High magnification of a foreign body granuloma around ova (o) of Schistosoma species, with several multi‐nucleated giant cells (gc). (b) Immunologically driven granulomas of sarcoidosis, with prominent multi‐nucleated giant cells (gc) and epithelioid cells (e), surrounded by collagenous connective tissue (ct). (c) A tuberculous granuloma in the lung, demonstrating central necrosis (n) surrounded by a zone of epithelioid cells (e), multi‐nucleated giant cells (gc) and lymphocytes (ly).


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Further Reading

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Kumar, Rakesh K, and Wakefield, Denis(Apr 2015) Inflammation: Chronic. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000944.pub4]