Mannan-binding lectin (MBL)-associated serine protease-1 (MASP-1), a serine protease associated with humoral pattern-recognition molecules: normal and acute-phase levels in serum and stoichiometry of lectin pathway components

Clin Exp Immunol. 2012 Jul;169(1):38-48. doi: 10.1111/j.1365-2249.2012.04584.x.


The pattern-recognition molecules mannan-binding lectin (MBL) and the three ficolins circulate in blood in complexes with MBL-associated serine proteases (MASPs). When MBL or ficolin recognizes a microorganism, activation of the MASPs occurs leading to activation of the complement system, an important component of the innate immune system. Three proteins are produced from the MASP1 gene: MASP-1 and MASP-3 and MAp44. We present an assay specific for MASP-1, which is based on inhibition of the binding of anti-MASP-1-specific antibody to MASP-1 domains coated onto microtitre wells. MASP-1 was found in serum in large complexes eluting in a position corresponding to ∼600 kDa after gel permeation chromatography in calcium-containing buffer and as monomers of ∼75 kDa in dissociating buffer. The concentration of MASP-1 in donor sera (n = 105) was distributed log-normally with a median value of 11 µg/ml (range 4-30 µg/ml). Serum and citrate plasma levels were similar, while the values in ethylenediamine tetraacetic acid plasma were slightly lower and in heparin plasma were 1·5 times higher than in serum. MASP-1 was present at adult level at 1 year of age, while it was 60% at birth. In normal healthy individuals the level of MASP-1 was stable throughout a 2-month period. After induction of an acute-phase reaction by operation we found an initial short decrease, concomitant with an increase in C-reactive protein levels, followed by an increase, doubling the MASP-1 concentration after 2 days. The present data prepare the ground for studies on the associations of MASP-1 levels with disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute-Phase Reaction / blood*
  • Acute-Phase Reaction / immunology*
  • Adult
  • Age Factors
  • Animals
  • Blotting, Western / methods
  • C-Reactive Protein / analysis
  • Chromatography, Gel / methods
  • Colorectal Neoplasms / blood
  • Complement Pathway, Mannose-Binding Lectin / immunology*
  • Humans
  • Immunity, Innate / immunology
  • Immunoglobulin G / isolation & purification
  • Infant
  • Infant, Newborn
  • Lectins / analysis
  • Lectins / immunology
  • Mannose-Binding Lectin / blood
  • Mannose-Binding Protein-Associated Serine Proteases / analysis*
  • Mannose-Binding Protein-Associated Serine Proteases / immunology*
  • Rats
  • Rats, Wistar


  • Immunoglobulin G
  • Lectins
  • Mannose-Binding Lectin
  • ficolin
  • C-Reactive Protein
  • MASP1 protein, human
  • Mannose-Binding Protein-Associated Serine Proteases