MBL is a key component in immune response in that it can directly trigger neutralization of invading microorganisms by an Ab-independent mechanism. Mutations of human MBL are associated with immunodeficiency resulting from a reduction in the ability of the mutant MBL to initiate complement fixation. In human, three types of MBL-associated serine proteases, MASP-1, MASP-2 and MASP-3, and a truncated form of MASP-2 (small MBL-associated protein; sMAP or MAp19) complex with MBL to activate the lectin pathway of the complement system. MASP-3 is an alternatively spliced product from the MASP-1 gene. The heavy/A chains are identical between MASP-1 and MASP-3 but the light/B chains are entirely different. Activated MASPs subsequently cleave and activate downstream components of the complement pathway.
C4/C2 activating component of Ra-reactive factor; Complement factor MASP-3; Complement-activating component of Ra-reactive factor; mannan-binding lectin serine peptidase 1 (C4/C2 activating component of Ra-reactive factor); Mannan-binding lectin serine protease 1; Mannan-binding lectin serine protease 1 heavy chain; Mannan-binding lectin serine protease 1 light chain; Mannose-binding lectin-associated serine protease 1; Mannose-binding protein-associated serine protease; MASP-1; Ra-reactive factor serine protease p100; RaRF; Serine protease 5