Cited by 625Wound Healing and TreatmentsDermatologic Treatments and ResearchLiver physiology and pathology

Immunology of Wound Healing

Open access
Ellis, Samantha, Lin, Elaine J., Tartar, Danielle·2018·Current Dermatology Reports

Abstract

PURPOSE OF REVIEW: Chronic wounds are a tremendous burden on the healthcare system and lead to significant patient morbidity and mortality. Normal cutaneous wound healing occurs through an intricate and delicate interplay between the immune system, keratinocytes, and dermal cells. Each cell type contributes signals that drive the normal phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. This paper reviews how various immunological cell types and signaling molecules influence the way wounds develop, persist, and heal. RECENT FINDINGS: Concurrent with the achievement of hemostasis, neutrophils are the first cells to migrate to the wound bed, brought in by pro-inflammatory signals including IL-8. Their apoptosis and engulfment by macrophages (efferocytosis) provides a key signal to the local immune milieu, including macrophages, to transition to an anti-inflammatory, pro-repair state, where angiogenesis occurs and granulation tissue is laid down. Myofibroblasts, activated through contractile forces and signaling molecules, then drive remodeling, where granulation tissue becomes scar. Unchecked inflammation at this stage can result in abnormal scar formation. SUMMARY: Although the derangement of immune signals at any stage can result in impaired wound healing, recent research has shown that the key transition point lies between the inflammatory and the proliferative phases. This review summarizes the events that facilitate this transition and discusses how this process can be disrupted, leading to chronic, non-healing wounds.

AI snapshot

Written from the paper’s full text.

TL;DR

This review summarizes immune mechanisms across hemostasis, inflammation, proliferation, and remodeling, arguing that the critical transition from the inflammatory to the proliferative phase often fails in chronic wounds. It highlights neutrophil apoptosis/efferocytosis and macrophage polarization as key drivers of repair.

Key findings

  • Chronic wounds in the USA afflict approximately 6.5 million individuals and cost the healthcare system over 25 billion dollars annually; their mortality effect has been reported as comparable to cancer.
  • Normal wound healing is divided into hemostasis (minutes to hours), inflammation (days 1–3), proliferation and repair (days 4–21), and remodeling (days 21–365); the key inflammatory-to-proliferative transition occurs around days 2–5 and often fails in chronic wounds.
  • Neutrophils are early responders recruited by IL-8/CXCL8; their apoptosis and macrophage engulfment (efferocytosis) signal a shift to anti-inflammatory, pro-repair macrophages. Persistent neutrophils, NETs, proteases/MMPs, reactive oxygen species, and elevated CXCL8 contribute to chronic, non-healing wounds.
  • Anti-inflammatory macrophages promote angiogenesis, granulation tissue, and re-epithelialization via VEGF, TGF-β, PDGF, EGF, KGF, and other signals; impaired pro- to anti-inflammatory macrophage transition—seen with iron overload, hyperglycemia, and hypoxia—stalls healing. Mature scars regain only 80% of initial tensile strength.

Methods

  • Narrative review of the literature; no primary data, sample, or statistical analysis are reported.
  • Synthesizes immune cell and signaling pathways across the four phases of wound healing, focusing on the inflammatory-to-proliferative transition and chronic wounds.
  • Draws on cited animal models, in vitro studies, and human wound observations; no systematic search or meta-analysis is described.

Limitations

  • The paper states no limitations.
  • Evident from the text: it is a narrative review without systematic search, inclusion criteria, or quality appraisal.
  • Evident from the text: many mechanistic conclusions rely on mouse models and in vitro findings, with limited direct human chronic wound data; no original experiments or quantitative synthesis are presented.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1007/s13671-018-0234-9

Cites

103 of 103 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 81 cited sources checked · 0 supported · 0 flagged

  • Premisecitation

    In impaired models of wound healing such as diabetes, where infection risk is higher, neutrophils are clearly required.

    “In impaired models of wound healing, such as diabetes, where infection risk is higher, neutrophils are clearly required [28].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [28] Wilgus TA, Roy S, McDaniel JC. Neutrophils and wound repair: positive actions and negative reactions. Adv Wound Care. 2013;2(7):379–88. https://doi.org/10.1089/wound.2012.0383 . source

      Not checked in the free run.

    • Rests on an assumption: Findings from mouse models of wound healing can be generalized to human wound healing and chronic wounds.
  • Premisecitation

    Neutrophil influx into a wound is mediated by chemical signals including IL-8/CXCL8.

    “Their influx is mediated by a number of chemical signals, including IL-8, or CXCL8, as mentioned above, and neutrophils have over 30 different receptors that mitigate their migration and activation response [24].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [24] Futosi K, Fodor S, Mocsai A. Neutrophil cell surface receptors and their intracellular signal transduction pathways. Int Immunopharmacol. 2013;17(3):638–50. https://doi.org/10.1016/j.intimp.2013.06.034 . source

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  • Premisecitation

    Normal wound healing can generally be broken down into four overlapping but distinct steps: hemostasis, inflammation, proliferation and repair, and wound remodeling.

    “normal wound healing can generally be broken down into four over-lapping but distinct steps (Fig. 1). These steps include hemostasis (minutes to hours after injury), inflammation (days 1–3), proliferation and repair (days 4–21), and lastly, wound remodeling (days 21–365) [8, 9].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [8] Morton LM, Phillips TJ. Wound healing and treating wounds: differential diagnosis and evaluation of chronic wounds. J Am Acad Dermatol. 2016;74(4):589–605; quiz −6. https://doi.org/10.1016/j.jaad.2015.08.068 . source

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    • cites [9] Reinke JM, Sorg H. Wound repair and regeneration. Eur Surg Res. 2012;49(1):35–43. https://doi.org/10.1159/000339613 . source

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  • Premisecitation

    Chronic wounds demonstrate significantly increased levels of the potent neutrophil chemoattractant CXCL8.

    “chronic wounds demonstrate significantly increased levels of the potent neutrophil chemoattractant, CXCL8 [58].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [58] Fivenson DP, Faria DT, Nickoloff BJ, Poverini PJ, Kunkel S, Burdick M, et al. Chemokine and inflammatory cytokine changes during chronic wound healing. Wound Repair Regen. 1997;5(4):310–22. https://doi.org/10.1046/j.1524-475X.1997.50405.x . source

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  • Premisereasoning

    Platelet activation releases growth factors such as PDGF and immune mediators responsible for activation of the immune system and transition to the inflammatory phase.

    “Platelet activation not only results in hemostasis, but also in the release of growth factors such as platelet-derived growth factor (PDGF) as well as immune mediators that are responsible for activation of the immune system and transition to the inflammatory phase of wound healing.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 15
  • May combine two claims.

    Premisecitation

    Neutrophils are the first cells to migrate to the wound bed, brought in by pro-inflammatory signals including IL-8.

    “Concurrent with the achievement of hemostasis, neutrophils are the first cells to migrate to the wound bed, brought in by pro-inflammatory signals including IL-8.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [31] Baggiolini M, Loetscher P, Moser B. Interleukin-8 and the chemokine family. Int J Immunopharmacol. 1995;17(2):103–8. source

      Not checked in the free run.

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    Premisecitation

    Neutrophils are the most abundant inflammatory cells to infiltrate a new wound and function mainly to remove debris and prevent infection.

    “Neutrophils represent the most abundant inflammatory cells to infiltrate a new wound and function mainly to remove debris and prevent infection [22, 23].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [22] Engelhardt E, Toksoy A, Goebeler M, Debus S, Brocker EB, Gillitzer R. Chemokines IL-8, GROalpha, MCP-1, IP-10, and Mig are sequentially and differentially expressed during phase-specific infiltration of leukocyte subsets in human wound healing. Am J Pathol. 1998;153(6):1849–60. source

      Not checked in the free run.

    • cites [23] de Oliveira S, Rosowski EE, Huttenlocher A. Neutrophil migration in infection and wound repair: going forward in reverse. Nat Rev Immunol. 2016;16(6):378–91. https://doi.org/10.1038/nri.2016.49 . source

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    Premisecitation

    NETs are detected in excess in diabetic foot wounds and delay healing, and inhibition of NETosis and NET function in mouse models of delayed wound healing improves outcomes.

    “NETs have also been detected in excess in diabetic foot wounds and have been shown to delay healing, and inhibition of NETosis and NET function in mouse models of delayed wound healing improves outcomes [59•].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [59•]

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    • Rests on an assumption: Findings from mouse models of wound healing can be generalized to human wound healing and chronic wounds.
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    Premisecitation

    Macrophages play a critical role in wound healing, including in angiogenesis, fibroplasia, cell proliferation, and transition out of the inflammatory phase.

    “Macrophages play a critical role in wound healing, and their roles in angiogenesis, fibroplasia, cell proliferation, and transition out of the inflammatory phase is clear (Fig. 2) [25–27, 60].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [25] Leibovich SJ, Ross R. The role of the macrophage in wound repair. A study with hydrocortisone and antimacrophage serum. Am J Pathol. 1975;78(1):71–100.

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    • cites [26] Pinhal-Enfield G, Ramanathan M, Hasko G, Vogel SN, Salzman AL, Boons GJ, et al. An angiogenic switch in macrophages involving synergy between Toll-like receptors 2, 4, 7, and 9 and adenosine A(2A) receptors. Am J Pathol. 2003;163(2):711–21. https://doi.org/10.1016/s0002-9440(10)63698-x . source

      Not checked in the free run.

    • cites [27] Simpson DM, Ross R. The neutrophilic leukocyte in wound repair a study with antineutrophil serum. J Clin Invest. 1972;51(8):2009–23. https://doi.org/10.1172/jci107007 . source

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  • May combine two claims.

    Premisecitation

    The inflammatory phase overlaps considerably with initial hemostasis and occurs during the first 72 h after tissue injury.

    “The inflammatory phase overlaps considerably with initial hemostasis, occurring during the first 72 h after tissue injury [16].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [16] Eming SA, Martin P, Tomic-Canic M. Wound repair and regeneration: mechanisms, signaling, and translation. Sci Transl Med. 2014;6(265):265sr6. https://doi.org/10.1126/scitranslmed.3009337 . source

      Not checked in the free run.

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    Premisecitation

    Histamine released by the activated complement cascade causes capillary dilation and leakage, accelerating migration of inflammatory cells and full transition to the inflammatory phase.

    “After hemostasis is achieved, histamine released by the activated complement cascade causes capillary dilation and leakage, accelerating migration of inflammatory cells into the wound bed and full transition to the inflammatory phase of wound healing [15].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] Sinno H, Prakash S. Complements and the wound healing cascade: an updated review. Plast Surg Int. 2013;2013:146764–7. https://doi.org/10.1155/2013/146764 . source

      Not checked in the free run.

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    Premisecitation

    Neutrophil-derived proteases such as elastase and matrix metalloproteinases can degrade healthy extracellular matrix, and increased levels of these proteases have been repeatedly detected in chronic wounds.

    “neutrophil-derived proteases, such as elastase and matrix metalloproteinases (MMPs), can degrade healthy extracellular matrix (ECM), and increased levels of these proteases have been repeatedly detected in chronic wounds [52–56].”
    Quote in the paperSubstantial claim0 of 5 sources checked
    • cites [52] Briggaman RA, Schechter NM, Fraki J, Lazarus GS. Degradation of the epidermal-dermal junction by proteolytic enzymes from human skin and human polymorphonuclear leukocytes. J Exp Med. 1984;160(4):1027–42. source

      Not checked in the free run.

    • cites [53] Grinnell F, Zhu M. Fibronectin degradation in chronic wounds depends on the relative levels of elastase, alpha1-proteinase inhibitor, and alpha2-macroglobulin. J Invest Dermatol. 1996;106(2):335–41. source

      Not checked in the free run.

    • cites [54] Herrick S, Ashcroft G, Ireland G, Horan M, McCollum C, Ferguson M. Up-regulation of elastase in acute wounds of healthy aged humans and chronic venous leg ulcers are associated with matrix degradation. Lab Invest. 1997;77(3):281–8.

      Not checked in the free run.

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      Not checked in the free run.

    • cites [56] Pirila E, Korpi JT, Korkiamaki T, Jahkola T, Gutierrez-Fernandez A, Lopez-Otin C, et al. Collagenase-2 (MMP-8) and matrilysin-2 (MMP-26) expression in human wounds of different etiologies. Wound Repair Regen. 2007;15(1):47–57. https://doi.org/10.1111/j.1524-475X.2006.00184.x . source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Platelet degranulation releases inflammatory mediators including IL-8/CXCL8, IL-1α, IL-1β, IL-6, and TNF-α, and activates the complement cascade.

    “Platelet degranulation also leads to the release of inflammatory mediators such as interleukin (IL)-8, or CXCL8 (a potent neutrophil chemoattractant), in addition to IL-1α, IL-1β, IL-6, and tumor necrosis factor (TNF)-α, and activates the complement cascade [9, 14].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [9] Reinke JM, Sorg H. Wound repair and regeneration. Eur Surg Res. 2012;49(1):35–43. https://doi.org/10.1159/000339613 . source

      Not checked in the free run.

    • cites [14] Bjork J, Hugli TE, Smedegard G. Microvascular effects of anaphylatoxins C3a and C5a. J Immunol. 1985;134(2):1115–9. source

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    Premisecitation

    Dysregulation of hemostasis, inflammation, proliferation, or remodeling can result in delayed wound healing and the potential to form chronic ulcers and/or excessive scarring.

    “Dysregulation of any of these events can result in delayed wound healing and the potential to form chronic ulcers and/or excessive scarring [10••].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10••]

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    Premisecitation

    Anti-inflammatory, pro-repair macrophages produce VEGF, which promotes vessel sprouting, and express two transmembrane proteins that promote vascular anastomosis.

    “Not only do anti-inflammatory, pro-repair macrophages produce VEGF, which promotes vessel sprouting, they also express two transmembrane proteins that have been shown to promote vascular anastomosis [80, 85, 86].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [80] Brancato SK, Albina JE. Wound macrophages as key regulators of repair: origin, phenotype, and function. Am J Pathol. 2011;178(1):19–25. https://doi.org/10.1016/j.ajpath.2010.08.003 . source

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    • cites [85] Fantin A, Vieira JM, Gestri G, Denti L, Schwarz Q, Prykhozhij S, et al. Tissue macrophages act as cellular chaperones for vascular anastomosis downstream of VEGF-mediated endothelial tip cell induction. Blood. 2010;116(5):829–40. https://doi.org/10.1182/blood-2009-12-257832 . source

      Not checked in the free run.

    • cites [86] Affolter M, Zeller R, Caussinus E. Tissue remodelling through branching morphogenesis. Nat Rev Mol Cell Biol. 2009;10:831–42. https://doi.org/10.1038/nrm2797 . source

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    Premisecitation

    Wounds without IL-6 lack an appropriate inflammatory response and demonstrate stunted angiogenesis, collagen accumulation, and re-epithelialization.

    “Wounds without IL-6 lack an appropriate inflammatory response and demonstrate stunted angiogenesis, collagen accumulation, and re-epithelialization [89].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [89] Lin ZQ, Kondo T, Ishida Y, Takayasu T, Mukaida N. Essential involvement of IL-6 in the skin wound-healing process as evidenced by delayed wound healing in IL-6-deficient mice. J Leukoc Biol. 2003;73(6):713–21. source

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  • May combine two claims.

    Interpretationcitation

    When the transition from a pro-inflammatory to an anti-inflammatory macrophage phenotype is impaired, wound healing stalls in the inflammatory phase and a chronic wound results.

    “When the transition from a pro- to an anti-inflammatory macrophage phenotype is impaired, wound healing stalls in the inflammatory phase and a chronic wound results [10••].”
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    • cites [10••]

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    Premisenone given

    Hyperglycemia in diabetes, hypoxia in arterial or venous insufficiency, or secondary infection likely also contribute to the persistence of pro-inflammatory macrophages.

    “Additional signals, such as hyperglycemia in the setting of diabetes, hypoxia in the setting of arterial or venous insufficiency, or secondary infection likely also contribute to the persistence of pro-inflammatory macrophages.”
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    Interpretationreasoning

    If wounds fail to transition from the inflammatory phase, pro-inflammatory macrophages persist and non-healing wounds develop.

    “If wounds fail to transition from the inflammatory phase, pro-inflammatory macrophages persist and non-healing wounds develop.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationnone given

    Numerous signals are responsible for the transition between the inflammatory and proliferative phases, most notably the apoptosis and phagocytosis of wound-bed resident neutrophils (efferocytosis).

    “Numerous signals are responsible for the transition, most notably the apoptosis and phagocytosis of wound-bed resident neutrophils (efferocytosis).”
    Quote in the paperNot a substantial claim
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  • The paper relies on this without support.

    Findings from mouse models of wound healing can be generalized to human wound healing and chronic wounds.

    “mouse models of wound healing have shown that in non-aged, non-impaired models, neutrophil depletion does not negatively affect wound healing as profoundly as macrophage deletion [25–27].”
    “in a mouse model of iron overload, local wound macrophages persisted in a pro-inflammatory state with excess production of inducible nitric oxide synthase (iNOS), IL-12, and TNF-α, in addition to free radicals, leading to impaired wound healing [81].”
    “inhibition of NETosis and NET function in mouse models of delayed wound healing improves outcomes [59•].”
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Authors
Ellis, S., Lin, E. J., & Tartar, D.
Affiliations
University of California, Davis (US)
Corresponding author
Tartar, Danielle
Venue
Current Dermatology Reports
Published
2018-09-28
Volume
7
Issue
4
Pages
350-358
ISSN
2162-4933 (ISSN-L)
OpenAlex
W2892642834
Cited by
625
References
105
Citations by year
2026: 65 · 2025: 114 · 2024: 109 · 2023: 90 · 2022: 96 · 2021: 86 · 2020: 44 · 2019: 21
FWCI
4.74
Type
journal article
Language
en
Open access
Locations
  • Current Dermatology Reports (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, other-oa)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • eScholarship (California Digital Library) (submittedVersion, cc-by)
Topics
  • Health Sciences › Medicine › Rehabilitation › Wound Healing and Treatments
  • Health Sciences › Medicine › Dermatology › Dermatologic Treatments and Research
  • Health Sciences › Medicine › Hepatology › Liver physiology and pathology
Keywords
wound healing, chronic wounds, skin wound healing, neutrophils, efferocytosis, macrophages, interleukin-8, inflammation, angiogenesis, granulation tissue, myofibroblasts, scar formation, keratinocytes, dermal cells, immune signaling

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