Anti-CD74 molecule antibodies are directed against the protein encoded by the gene CD74 in humans. The gene may also be known as Ia-GAMMA, DHLAG, HLADG, II, and HLA class II histocompatibility antigen gamma chain. Structurally, the protein is reported to be 33.5 kilodaltons in mass. Based on gene name, canine, porcine, monkey, mouse, and rat orthologs may also be found.