Factor B is a component of the alternative pathway of complement activation. The protein consists of a single polypeptide chain of molecular mass 93 kDa, and has a concentration in plasma of appro, Xenopus/Amphibian,imately 200 ,mg/mL. Factor B is cleaved by factor D into the Ba component (30 kDa) and the Bb (63 kDa). Together with C3Bovine, Bb forms the alternative pathway C3 convertase C3bBb. This antibody is specific for the Bb fragment of human factor B. Antibody binding abolishes the formation of C3bBb comple, Xenopus/Amphibian,es.