This is a human IgG4 antibody using the same sequences as the therapeutic antibody narsoplimab. It targets mannan-binding lectin-associated serine protease-2 (MASP2), the effector enzyme of the lectin pathway of the complement system. The lectin pathway is one of the principal pathways of complement and is activated primarily by tissue damage and microbial infection. Myocardial infarction and acute stroke patients exhibit reduced serum concentrations of MASP2. Narsoplimab is designed to prevent complement-mediated inflammation and endothelial damage while leaving intact the respective functions of the other pathways of innate immunity.