The ficolins and mannose-binding lectin (MBL) are collagen-like defence proteins 
that serve as recognition molecules in lectin complement pathway. Differential 
features that may indicate diverse functions of these proteins are poorly 
understood. In this study we compared important biological features of the 
ficolins and MBL. We investigated the tissue distribution of the FCN1-3 and the 
MBL2 genes encoding the ficolins and MBL by quantitative PCR. Recombinant 
proteins were produced and structural and biological characteristics were 
investigated and compared. Our main findings were that FCN3 mRNA was highly 
expressed in the liver and lung compared with the other genes revealing the lung 
as the tissue with the highest FCN3 expression pattern. Ficolin-3 revealed 
higher complement activating capacity compared with Ficolin-2, MBL and Ficolin-1 
and was highly resistant to bacterial collagenase treatment, which is different 
from the other ficolins and MBL. We discovered several unique properties of 
Ficolin-3 showing that FCN3 is the most highly expressed gene in liver and lung 
among the lectin complement pathway initiators. Moreover, Ficolin-3 has a high 
complement activating potential and is the only collagenase proteolytic 
resistant molecule among the lectin complement pathway initiators.