Anti-Complement factor B antibodies are used in the immunodetection of the protein encoded by the CFB gene. In humans, the canonical protein has a reported length of 764 amino acid residues and a mass of 85.5 kDa. It is known to be a secreted protein. Alternative splicing is reported to yield 2 different isoforms for this protein. A member of the Peptidase S1 protein family, it is reported to be a Factor B, which is part of the alternate pathway of the complement system is cleaved by factor D into 2 fragments: Ba and Bb. Post-translational modifications have been described, including glycosylation. Other names for this target antigen include AHUS4 and ARMD14.