Notably, B2M encodes the well characterized β2-microglobulin, a molecular chaperone known to form complexes with multiple partners, including HLA, HFE, FcRn, MR1 (Human Leukocyte Antigen, Hereditary hemochromatosis protein, Neonatal Fc Receptor and Major histocompatibility complex class I-related gene protein). The gene discussed is MR1; the disease is hemochromatosis type 1.