Anti-fibrosin like 1 antibodies are used in the immunodetection of the protein encoded by the FBRSL1 gene. In humans, the canonical protein has a reported length of 1045 amino acid residues and a mass of 110.9 kDa. The fibrosin like 1 protein is a member of the AUTS2 protein family. Other names for this target antigen include AUTS2-like protein, HBV X-transactivated gene 9 protein, HBV XAg-transactivated protein 9, and fibrosin-1-like protein.