Inflammation and Healing
Inflammation and healing are the linked tissue responses to injury and infection. Inflammation is the protective reaction that delivers blood cells and plasma proteins to a site of damage; healing is the subsequent process by which the damaged tissue is repaired, either by regeneration of native cells or by replacement with connective-tissue scar. This area orients the reader to acute and chronic inflammation, the special pattern of granulomatous inflammation, and the repair end-states of regeneration and fibrosis.
Definition
Inflammation and healing denote, respectively, the vascular and cellular response to injurious stimuli and the restorative response that follows, encompassing acute and chronic inflammation, granuloma formation, tissue regeneration, and fibrosis.
Scope
The area covers the general pathology of the inflammatory and reparative responses as a unified theme: how acute inflammation is initiated and resolved, how persistent injury produces chronic inflammation, how granulomas form around indigestible or persistent stimuli, and how the outcome of injury is decided between regeneration and fibrous scarring. It is a reference overview of mechanisms rather than a guide to managing any specific inflammatory disease.
Sub-topics
Core questions
- How does the body recognise injury and mount an acute inflammatory response?
- Why do some inflammatory responses resolve while others become chronic?
- What determines whether injured tissue regenerates or heals by scar?
Key concepts
- Acute versus chronic inflammation
- Vascular and cellular phases of inflammation
- Resolution and non-resolving inflammation
- Granuloma formation
- Regeneration versus repair by scar
- Fibrosis as an outcome of persistent injury
Mechanisms
Tissue injury and microbial products are sensed by resident cells, triggering release of mediators that increase vascular permeability and recruit leukocytes — the acute inflammatory response. When the inciting stimulus is cleared, pro-resolving mechanisms terminate the reaction and healing begins; when it persists, the response becomes chronic, dominated by mononuclear cells and accompanied by simultaneous tissue destruction and repair. Repair proceeds either by regeneration, in which parenchymal cells replace those lost, or by connective-tissue deposition that forms a scar. Macrophages are central throughout, helping to drive both the inflammatory and the reparative phases and, when repair is excessive, contributing to fibrosis (Medzhitov, 2008; Gurtner, 2008; Wynn, 2016; Nathan, 2010).
Clinical relevance
Inflammation and healing underlie the tissue changes seen across infectious, autoimmune, ischaemic, and degenerative disease, and the balance between resolution and chronicity helps explain why some conditions heal and others progress to organ damage. This area describes those general mechanisms for reference and education and is not a source of diagnostic or treatment recommendations.
Evidence & guidelines
The mechanistic account summarised here rests on a large experimental and review literature and on standard pathology references such as Robbins & Cotran Pathologic Basis of Disease (Kumar, Abbas, & Aster, 2021). As a basic-science area it is not governed by clinical practice guidelines; recommendations belong to the disease-specific entries that build on these principles.
History
The cardinal signs of inflammation were described in antiquity and refined through nineteenth-century cellular pathology, when Julius Cohnheim characterised the vascular events and Élie Metchnikoff identified phagocytosis. The twentieth century added the chemical mediators and leukocyte biology, and contemporary work has reframed inflammation as an actively resolved program whose failure to terminate links it to chronic disease and fibrosis (Medzhitov, 2008; Nathan, 2010).
Key figures
- Ruslan Medzhitov
- Carl Nathan
- Thomas A. Wynn
- Geoffrey C. Gurtner
Related topics
Seminal works
- medzhitov-2008
- gurtner-2008
- nathan-2010
- wynn-2016
Frequently asked questions
- What is the difference between inflammation and healing?
- Inflammation is the immediate defensive response that brings cells and proteins to a site of injury, whereas healing is the later process that restores the tissue, either by regenerating native cells or by forming a connective-tissue scar.
- Is inflammation always harmful?
- No. Acute inflammation is a protective, normally self-limiting response essential to defence and repair; harm arises chiefly when it is excessive or fails to resolve and becomes chronic.