Singh P B, Brown R E, Roser B
Nature. 1987;327(6118):161-4. doi: 10.1038/327161a0.
The classical class I antigens of the major histocompatibility complex (MHC) are cell-surface glycoproteins which were originally discovered because they cause rapid rejection of cells or tissues grafted between unrelated individuals. These molecules are encoded by the K, D and L loci of the mouse MHC (and analogous loci in other species) which show extreme species polymorphism and a large number of alleles. In an outbreeding population 3.6 X 10(9) unique MHC class I phenotypes can be encoded by the 100 alleles at each of the K and D loci and the 6 alleles at the L locus. This level of polymorphism ensures that the cells and tissues of each unrelated individual are uniquely identified by their class I membrane-bound antigens. Like other membrane bound proteins, these class I molecules are anchored in the lipid bilayer by a hydrophobic domain encoded by exon 5. However, there have been reports of the occurrence of classical class I molecules in true solution in the blood of humans, mice, and rats. We report here that classical polymorphic class I molecules in normal rats are constitutively excreted in the urine and that untrained rats can distinguish the smell of urine samples taken from normal donors that differ only at the class I MHC locus and therefore excrete different allelomorphs of class I molecules in their urine.
主要组织相容性复合体（MHC）的经典I类抗原是细胞表面糖蛋白，最初发现它们会导致在不相关个体之间移植的细胞或组织迅速被排斥。这些分子由小鼠MHC的K、D和L基因座（以及其他物种中的类似基因座）编码，这些基因座表现出极端的物种多态性和大量等位基因。在一个杂交群体中，K和D基因座各100个等位基因以及L基因座6个等位基因可编码3.6×10⁹种独特的MHC I类表型。这种多态性水平确保每个不相关个体的细胞和组织通过其I类膜结合抗原被独特识别。与其他膜结合蛋白一样，这些I类分子通过外显子5编码的疏水结构域锚定在脂质双层中。然而，已有报道称在人类、小鼠和大鼠的血液中有处于真溶液状态的经典I类分子。我们在此报告，正常大鼠体内的经典多态性I类分子会持续排泄到尿液中，且未经训练的大鼠能够区分仅在I类MHC基因座不同、因而尿液中排泄不同I类分子等位体的正常供体的尿液气味。
