Characterization of a polymorphism in the coding sequence of FCN3 resulting in a Ficolin-3 (Hakata antigen) deficiency state

Mol Immunol. 2008 May;45(9):2660-6. doi: 10.1016/j.molimm.2007.12.012. Epub 2008 Feb 7.


Ficolin-3 (Hakata antigen or H-ficolin) is a soluble pattern recognition molecule in the lectin complement pathway. We speculated whether common genetic variations in the FCN3 gene contribute to deficiency of Ficolin-3. The FCN3 gene was sequenced in 237 healthy Danish Caucasians. The relevance of polymorphisms was assessed with antibodies against Ficolin-3 in a novel ELISA system and by production of recombinant Ficolin-3 variants. Ficolin-3 serum profiles were analyzed by SDS-PAGE and western blotting. Ficolin-3 serum concentration varied 10-fold (median, 24microg/ml; range, 3-54microg/ml). Out of several polymorphisms one FCN3+1637delC causing a reading frame shift and a distortion of the C-terminal end of the molecule with an allele frequency of 0.011 was particularly interesting. In individuals heterozygous for the FCN3+1637delC deletion lowered Ficolin-3 concentration was observed (P=0.025). SDS-PAGE and western blotting of serum revealed a weak band corresponding to the truncated molecule in addition to the normal Ficolin-3 pattern. Characterization of recombinant Ficolin-3 derived from FCN3+1637delC showed that in the homozygous situation this allelic variant would lead to Ficolin-3 deficiency. In conclusion an FCN3+1637delC deletion variant disrupting the possibility for pattern recognition was detected. Characterization of recombinant variant Ficolin-3 shows that homozygosity for the FCN3+1637delC deletion may lead to Ficolin-3 deficiency and may thus be the basis for a novel complement deficiency state.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cell Line
  • Enzyme-Linked Immunosorbent Assay
  • Exons
  • Glycoproteins / blood
  • Glycoproteins / deficiency*
  • Glycoproteins / genetics*
  • Heterozygote
  • Homozygote
  • Humans
  • Lectins / blood
  • Lectins / deficiency*
  • Lectins / genetics*
  • Polymorphism, Genetic*
  • Promoter Regions, Genetic
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Analysis, DNA


  • FCN3 protein, human
  • Glycoproteins
  • Lectins
  • Recombinant Proteins