MASP2 encodes a serine protease that serves as a key effector enzyme in the lectin pathway of complement activation, catalyzing cleavage and activation of complement components C2 and C4 1. As the effector component of mannose-binding lectin (MBL), MASP2 activates the complement system in an antibody-independent manner 2. The protein functions through calcium-dependent protein binding and exhibits serine-type endopeptidase activity in the extracellular region. MASP2 deficiency can lead to increased susceptibility to pyogenic infections and autoimmunity, though some individuals may remain asymptomatic 1. The gene shows significant disease relevance, with elevated serum MASP2 levels observed in systemic lupus erythematosus patients and demonstrating good diagnostic ability for lupus 3. Multiple genetic polymorphisms in MASP2 are associated with susceptibility to various conditions, including tuberculosis 4, HTLV-1 infection 2, and systemic lupus erythematosus 3. Clinically, MASP2 inhibition represents a therapeutic target, with narsoplimab (a MASP-2 inhibitor) showing efficacy in treating hematopoietic stem-cell transplantation-associated thrombotic microangiopathy and receiving FDA Breakthrough Therapy Designation 56. The protein is also being investigated as a potential therapeutic target in IgA nephropathy through lectin pathway complement inhibition 7.