Β2-微球蛋白

β2微球蛋白（英語：β2-microglobulin，缩写B2M）是MHC1類分子分子的组成部分之一，在所有有核的细胞中（即不包括红细胞）都有表达。在人类基因组中，β2微球蛋白由B2M 基因所编码。 β2-微球蛋白位于细胞表面的α3链旁，但与α链不同的是，β2并没有跨膜区域，且为非共价结合。在β2的“上方”（指远离细胞膜的一端）为α链的α1区和α2区，构成了MHC的肽结合区。 β2微球蛋白不止参与形成第一类MHC分子，还能组成与之类似的表面受体，如CD1和Qa（英语：Alloantigen）等。 β2微球蛋白还有一个功能，就是能与HFE蛋白（英语：HFE (gene)）结合，来调控铁调素在肝脏中的表达。鐵調素會與肠上皮细胞和巨噬细胞膜上的膜铁转运蛋白（英语：ferroportin）作用。可以降低食物中和紅血球回收的鐵質攝取，该功能的丧失会导致铁过量和血色沉著病。 在长期血液透析的患者中，β2微球蛋白可以聚集成淀粉样纤维沉积在关节间隙，这种疾病被称为透析相关淀粉样变性。 缺乏β2微球蛋白基因的小鼠模型已经被改造。这些小鼠证明β2微球蛋白对于MHC Ⅰ类分子的细胞表面表达和肽结合沟的稳定性是必需的。事实上，在没有β2微球蛋白的情况下，可以在表面检测到数量非常有限的MHC I类分子。在没有MHC I类分子的情况下，CD8 T细胞不能生长（CD8 T细胞是参与获得性免疫发展的T细胞的一个子集）。低水平的β2微球蛋白可显示HIV的非进展性。 多发性骨髓瘤和淋巴瘤的β-2微球蛋白水平可能升高，但在这些情况下，原发性淀粉样变性（淀粉样轻链）和继发性淀粉样变性（淀粉样相关蛋白）更常见。β-2微球蛋白的正常值为<2 mg/L。 然而，对于多发性骨髓瘤，β2微球蛋白的水平也可能处于谱的另一端。多发性骨髓瘤的诊断检测包括获取β2微球蛋白水平，因为该水平是一个重要的预后指标,水平<4 mg/L的患者的中位生存期预计为43个月，而水平>4 mg/L的患者的中位生存期仅为12个月。β-2微球蛋白水平不能区分预后较好的不确定意义的单克隆免疫球蛋白血症（英语：Monoclonal gammopathy of undetermined significance）（MGUS）和隐匿性（低度）骨髓瘤。 與Β2微球蛋白相關的疾病；在維基數據上查看/編輯參考.  GRCh38: Ensembl release 89: ENSG00000166710、​ENSG00000273686 - Ensembl, May 2017 GRCm38: Ensembl release 89: ENSMUSG00000060802 - Ensembl, May 2017 Human PubMed Reference:. 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