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 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 disease states 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 between cytokines that promote inflammatory cell recruitment/activation and growth factors that promote healing.