Anti-RETINOL BINDING PROTEIN 4 antibodies are used in the immunodetection of the protein encoded by the RBP4 gene. In humans, the canonical protein has a reported length of 201 amino acid residues and a mass of 23 kDa. It is known to be a secreted protein. It is notably expressed in blood plasma and in urine. A member of the Lipocalin protein family, it is reported to be a retinol-binding protein that mediates retinol transport in blood plasma. Other names for this target antigen include RDCCAS, PRBP, RBP, plasma retinol-binding protein, retinol binding protein 4, plasma, and MCOPCB10.