Anti-ID4 antibodies are used in the immunodetection of the protein inhibitor of DNA binding 4. In humans, the canonical protein has a reported length of 161 amino acid residues and a mass of 16.6 kDa. Its subcellular localization is in the nucleus. Among its functions, ID4 is involved with the differentiation of certain cell types. Synonyms for this target antigen include bHLHb27, DNA-binding protein inhibitor ID-4, class B basic helix-loop-helix protein 27, inhibitor of DNA binding 4, HLH protein, and IDB4.