 When activated, C5 is involved in activating host cells, thereby attracting pro-inflammatory immune cells, while also destroying cells by triggering pore formation.By inhibiting the complement cascade at this point, the normal, disease-preventing functions of proximal complement system are largely preserved, while the properties of C5 that promote inflammation and cell destruction are impeded.Eculizumab inhibits the cleavage of C5 by the C5 convertase into C5a a potent anaphylatoxin with prothrombotic and proinflammatory properties, and C5b, which then forms the terminal complement complex C5b-9 which also has prothrombotic and proinflammatory effects.