A recombinant protein similar or identical to human mannose-binding lectin (MBL) with antimicrobial activity. MBL is a plasma protein containing a carbohydrate recognition domain at one end and a collagen-like stalk domain at the other. The presence of multiple carbohydrate binding sites in a single molecule of MBL (also called mannose-binding protein, mannan-binding protein or or MBP) allows strong binding to mannose residues on the phospholipid bilayer of microbial pathogens. Upon binding, activation of the complement system leads to the deposition of complement components on the surface of the microorganisms (opsonisation), followed by their clearance by phagocytic cells. Administration of the agent to deficient individuals may restore lectin function in vivo.