Activation of the alternative complement pathway by fungal melanins

Á L. Rosas, R. S. MacGill, Joshua D. Nosanchuk, T. R. Kozel, A. Casadevall

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Melanins are complex biological pigments formed by the oxidative polymerization of phenolic and/or indolic compounds. These pigments have been implicated in the pathogenesis of some microbial infections, malignancies, degenerative disorders, and autoimmune diseases. Recent studies have demonstrated that melanins have antigenic and anti-inflammatory properties. These findings led us to further explore the interaction of melanins with the immune system. Melanin particles ("ghosts") were isolated from in vitro-melanized Cryptococcus neoformans cells and Aspergillus niger conidia and then incubated in normal human serum containing 125I-labeled complement C3. The results demonstrated deposition of C3 fragments onto the melanin ghosts as early as 1 min after incubation, with maximum deposition occurring after 12 min for C. neoformans-derived melanin ghosts and after 25 min for A. niger-derived melanin ghosts. The blocking of classical pathway activation did not affect the kinetics or total deposition of C3 onto the melanin ghosts, indicating that melanins activate complement through the alternative pathway. Immunofluorescence analysis of lungs from BALB/c mice injected intratracheally with C. neoformans-derived melanin ghosts demonstrated deposition of C3 fragments onto the ghosts. Small granulomas were also observed surrounding the ghosts. However, melanization of the C. neoformans cell wall did not alter the kinetics or total deposition of C3 fragments onto the fungal cells. The finding that melanin surfaces can activate the complement system suggests a potential mechanism for the pathogenesis of some degenerative and/or autoimmune processes that involve melanized cells as well as another potential role for melanin in the virulence of melanin-producing microorganisms.

Original languageEnglish (US)
Pages (from-to)144-148
Number of pages5
JournalClinical and Diagnostic Laboratory Immunology
Volume9
Issue number1
DOIs
StatePublished - 2002

Fingerprint

Alternative Complement Pathway
Melanins
Chemical activation
Cryptococcus neoformans
Aspergillus niger
Biological Pigments
Complement C3
Kinetics
Fungal Spores
Immune system
Aspergillus
Granuloma
Pigments
Polymerization
Microorganisms
Cell Wall
Autoimmune Diseases
Fluorescent Antibody Technique
Virulence

ASJC Scopus subject areas

  • Microbiology (medical)
  • Immunology and Allergy
  • Clinical Biochemistry
  • Immunology

Cite this

Activation of the alternative complement pathway by fungal melanins. / Rosas, Á L.; MacGill, R. S.; Nosanchuk, Joshua D.; Kozel, T. R.; Casadevall, A.

In: Clinical and Diagnostic Laboratory Immunology, Vol. 9, No. 1, 2002, p. 144-148.

Research output: Contribution to journalArticle

Rosas, Á L. ; MacGill, R. S. ; Nosanchuk, Joshua D. ; Kozel, T. R. ; Casadevall, A. / Activation of the alternative complement pathway by fungal melanins. In: Clinical and Diagnostic Laboratory Immunology. 2002 ; Vol. 9, No. 1. pp. 144-148.
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