Antimouse C5 monoclonal antibodies effectively inhibit complement activation in vivo. Wild-type, FL, and GL mice were injected with a monoclonal antibody specific toward murine C5 (BB5.1) or with a control antibody (135.8), biweekly 40 mg/kg intraperitoneally for 3 weeks. The plasma of treated mice was assessed for C5b-9-mediated hemolysis before, one week into, and at the end of treatment. Hemolytic activity of sera from anti-C5-treated mice were reduced almost to 0 but remained unchanged in the serum of mice treated with the control antibody. Hemolysis has been normalized to hemolysis obtained from normal mouse serum (Sigma Aldrich). Data represent mean ± SD.