MASP-2 is a MBL associated serine protease. Mannan-binding lectin (MBL) and ficolins, in complex with MASPs, are capable of activating the complement system, thus mediating the destruction of infectious agents. After oligomerisation of MBL (or L-Ficolin) MASP-2 will be bound and activated. Activated MASP-2 cleaves C4 and C2 and is crucial for the activation of downstream complement components. MASP-2 deficiency will result in an increased susceptibility for infections (e.g. leukemia patients in chemotherapy are at high risk of serious infections). Even more so then MBL deficiency, because MASP-2 is also required for complement activation by H- and L-ficolin. The ELISA detects MASP-2 in serum and plasma. The MASP-2 levels in plasma from healthy individuals range from 170 to 1196 ng/ml.