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What happens when acute inflammation does not remove the cause of tissue injury?

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Pathways of complement activation — inflammation The main function of complement proteins is to aid in the destruction of pathogens by piercing their outer membranes (cell lysis) or by making them more attractive to phagocytic cells such as macrophages (a process known as opsonization). Some complement components also promote inflammation by stimulating cells to release histamine and by attracting phagocytic cells to the site of infection.

When acute inflammation fails to eliminate the cause of tissue injury, or if the healing process is interfered with, the response may progress to chronic inflammation. This state is characterized by the persistent infiltration of the injury site by macrophages, lymphocytes, and plasma cells. Macrophages, in particular, are the principal cells involved and contribute to ongoing tissue damage and functional impairment.12

Alternatively, if the injurious agent is difficult to eliminate, the body may undergo suppuration, or the formation of pus. This process often leads to the development of an abscess—a structure where pus is contained within a membrane. Because abscesses are often inaccessible to the immune system and antibiotics, they can be difficult to treat and may require surgical intervention.34

In some instances, chronic inflammation manifests as granulomatous inflammation, marked by the formation of granulomas, which are small collections of modified macrophages. These outcomes depend on the nature of the tissue involved and the extent of the initial destruction.14