Human serum mannose-binding lectin (MBL)-associated serine protease-1 (MASP-1): determination of levels in body fluids and identification of two forms in serum

Clin Exp Immunol. 1997 Nov;110(2):317-23. doi: 10.1111/j.1365-2249.1997.tb08334.x.


We developed an ELISA for human serum MASP-1, a C1s-like serine protease which is known to function in C4 and C2 activation. We then determined MASP-1 levels in 1063 sera from normal Japanese subjects ranging in age from 3 to 100 years, as well as in certain body fluids using this assay. Individual serum MASP-1 levels ranged from 1.48 to 12.83 microg/ml, with a normal frequency distribution pattern. The arithmetic mean +/- s.d. of MASP-1 levels in serum was 6.27 +/- 1.85 microg/ml, whereas levels of MASP-1 in cerebrospinal fluid and in urine were almost undetectable. When the mean +/- s.d. of serum MASP-1 was calculated for each age group (10 year range) and values were then compared, the age group consisting of 3-9-year-olds (7.54 +/- 1.39 microg/ml) was found to have the highest value. When MASP-1 was measured in cord blood, it was shown that levels were already as high as those of 3-9-year-olds. The serum MASP-1 level was found to be as strongly dependent on age as is the serum MBL level. MASP-1 and MBL are thought to play an active part in immunity in younger people. It was found that the serum level of MASP-1 was much higher than that of MBL, and the major portion of human serum MASP-1 appeared to exist in the circulation as a form unbound to MBL.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aging / blood
  • Body Fluids / enzymology
  • Child
  • Child, Preschool
  • Enzyme-Linked Immunosorbent Assay / methods*
  • Female
  • Humans
  • Male
  • Mannose-Binding Protein-Associated Serine Proteases
  • Middle Aged
  • Serine Endopeptidases / blood*


  • MASP2 protein, human
  • Mannose-Binding Protein-Associated Serine Proteases
  • Serine Endopeptidases