Lanzavecchia A, Reid P A, Watts C
Basel Institute for Immunology, Switzerland.
Nature. 1992 May 21;357(6375):249-52. doi: 10.1038/357249a0.
Functional, morphological and biochemical evidence indicates that class II major histocompatibility complex (MHC) molecules associate with processed peptides during biosynthesis. Peptide/MHC complexes in living cells have been reported to be less stable than similar complexes generated in vitro, which has led to the suggestion that there may be a peptide exchange mechanism operating in vivo. Although this could increase the capacity for binding incoming antigens, it would reduce the efficacy of processed antigenic peptides by exchanging these for self peptides. Here we measure the half-life of peptide/class II complexes in human antigen-presenting cells and find that it is very similar to the half-life of class II molecules themselves, indicating that peptides are bound irreversibly under physiological conditions. Thus class II MHC retains long-term 'memory' of past encounters with antigen to maximize the opportunity for T cell/antigen-presenting cell interaction.
功能、形态学和生物化学证据表明，II类主要组织相容性复合体（MHC）分子在生物合成过程中与加工后的肽段结合。据报道，活细胞中的肽/MHC复合物比体外产生的类似复合物稳定性更低，这表明体内可能存在一种肽交换机制。尽管这可能会增加结合外来抗原的能力，但通过将加工后的抗原肽替换为自身肽，会降低其效力。在这里，我们测量了人类抗原呈递细胞中肽/II类复合物的半衰期，发现它与II类分子本身的半衰期非常相似，这表明在生理条件下肽段是不可逆结合的。因此，II类MHC保留了过去与抗原接触的长期“记忆”，以最大限度地增加T细胞/抗原呈递细胞相互作用的机会。
