C5 and paroxysmal nocturnal hemoglobinuria: Eculizumab, a humanized monoclonal antibody that blocks the cleavage of C5, has demonstrated clinical efficacy in the treatment of complement-mediated diseases such as paroxysmal nocturnal hemoglobinuria (PNH) [5,27], atypical hemolytic uremic syndrome (aHUS) [28], and generalized myasthenia gravis [29].