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低分子量IgM(Low molecular weightIgM,LMW IgM)是自然出现并存于低等脊椎动物和新生儿血中的一种单体IgM。在健康成人,LMWIgM仅存在B淋巴细胞浆内和胞膜上。胞浆内LMWIgM是五聚体IgM的组成亚单位之一,在B淋巴细胞分泌IgM之前五个单体IgM与J链合成五聚体形式,分泌至血循环中。五聚体IgM的分子量约10Kd,沉降系数为19s,其理化特性及生物学功能已较清楚。胞膜上的LMWIgM是淋巴细胞的受体之一,可接受各种抗原的刺激,是特异性免疫反应的基础。自1963年Killander等在成人血清中发现LMWIgM以来,LMWlgM的研究进展也较快。本文拟就近些年来这些方面的研究综述如下。
Low Molecular Weight IgM (LMW IgM) is a monomeric IgM that occurs naturally in lower vertebrate and neonatal blood. In healthy adults, LMWIgM is present only on the plasma and on the membrane of B lymphocytes. The intracytoplasmic LMWIgM is one of the constituent subunits of pentameric IgM. Five monomeric IgM and pentagonal pentamers form before secretion of IgM by B lymphocytes and are secreted into the blood circulation. The molecular weight of pentameric IgM is about 10Kd and the sedimentation coefficient is 19s. The physical and chemical properties and biological functions of pentameric IgM have been clarified. LMWIgM on the cell membrane is one of the receptors for lymphocytes and can be stimulated by various antigens and is the basis of a specific immune response. Since 1963 when Killander et al found LMWIgM in adult serum, LMWlgM studies have progressed rapidly. This article intends to summarize these aspects in recent years as follows.