Anti-Cyclin D1 antibodies are directed against the protein encoded by the gene CCND1 in humans. The Cyclin D1 protein has a reported amino acid length of 295 and an expected mass of 33.7 kDa. The protein may also be known as BCL1, D11S287E, PRAD1, U21B31, G1/S-specific cyclin-D1, and B-cell CLL/lymphoma 1. Variants of this antigen may also be found in other species, including canine, porcine, monkey, mouse and rat.