Protective and inactivating effects of neutrophil myeloperoxidase on C1q activity

Giuliano Zabucchi, Renzo Menegazzi, Lucia Roncelli, Paolo Bertoncin, Francesco Tedesco, Pierluigi Patriarca

Research output: Contribution to journalArticlepeer-review


This study investigated the interaction between neutrophil myeloperoxidase (MPO) and the C1q component of the complement system. Using a dot-spot assay, MPO was found to bind to C1q in a dose-dependent manner. The specificity of this reaction was proved by the inhibitory effect of F(ab')2 antibodies to C1q and by the inability of MPO to bind to Clr, Cls and IgG. The interaction between MPO and C1q did not influence the enzymatic activity of the peroxidase but resulted in a more stable C1q as assessed by hemolytic assay for C1q. The protective effect of MPO on C1q did not require the presence of H2O2 in the reaction mixture nor was it inhibited by sodium azide, whereas it was abolished by heating the peroxidase. Lactoferrin and lysozyme, unlike MPO, were ineffective in protecting C1q from functional decay. Addition of H2O2 and chloride to MPO and C1q led to a complete inactivation of C1q, which could not be induced by H2O2 alone. The hypochlorite, which is known to be generated during the reaction of MPO with H2O2 and chloride, exhibited a similar inactivating effect on C1q, which was prevented by an external source of methionine.

Original languageEnglish
Pages (from-to)41-53
Number of pages13
Issue number1
Publication statusPublished - Feb 1990

ASJC Scopus subject areas

  • Medicine(all)
  • Immunology
  • Cell Biology


Dive into the research topics of 'Protective and inactivating effects of neutrophil myeloperoxidase on C1q activity'. Together they form a unique fingerprint.

Cite this