Β2微球蛋白

β2微球蛋白是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。

结构功能

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等。

β2微球蛋白还有一个功能，就是能与结合，来调控在肝脏中的表达，which targets the iron transporter on the cytoplasmic membrane of 肠上皮细胞和巨噬细胞 for degradation resulting in decreased iron uptake from food and iron release from recycled red blood cells respectively. 该功能的丧失会导致铁过量和血色沉着病。

临床意义

In patients on long-term hemodialysis, it can aggregate into amyloid fibers that deposit in joint spaces, a disease known as dialysis-related amyloidosis.

Mice models deficient for the β₂ microglobulin gene have been engineered. These mice demonstrate that β₂ microglobulin is necessary for cell surface expression of MHC class I and stability of the peptide binding groove. In fact, in the absence of β₂ microglobulin, very limited amounts of MHC class I (classical and non-classical) molecules can be detected on the surface. In the absence of MHC class I, CD8 T cells cannot develop. (CD8 T cells are a subset of T cells involved in the development of acquired immunity.) Low levels of β₂ microglobulin can indicate non-progression of HIV.

Levels of beta-2 microglobulin can be elevated in multiple myeloma and lymphoma, though in these cases primary amyloidosis (amyloid light chain) and secondary amyloidosis (amyloid associated protein) are more common. The normal value of beta-2 microglobulin is <2 mg/L. However, with respect to multiple myeloma, the levels of beta2-microglobulin may also be at the other end of the spectrum. Diagnostic testing for multiple myeloma includes obtaining the beta2-microglobulin level, for this level is an important prognostic indicator. A patient with a level <4 mg/L is expected to have a median survival of 43 months, while one with a level >4 mg/L has a median survival of only 12 months. Beta-2 microglobulin levels cannot, however, distinguish between monoclonal gammopathy of uncertain significance (MGUS), which has a better prognosis, and smouldering (low grade) myeloma.

外部链接

这是一篇与方剂相关的条目。推荐您访问中医智库，查看权威Β2微球蛋白信息。

这是一篇与医籍相关的条目。推荐您访问中医智库，阅读《Β2微球蛋白》经典原文。