Marchalonis J J, Cone R E, Atwell J L
J Exp Med. 1972 Apr 1;135(4):956-71. doi: 10.1084/jem.135.4.956.
Immunoglobulins were isolated from the surfaces of lymphocytes from a variety of lymphocyte populations including murine and human thymus lymphocytes and murine spleen and thoracic duct lymphocytes. Cell surface proteins were labeled with iodide-(125)I by lactoperoxidase-catalyzed iodination, and recovered in solution either by solubilization in dissociating solvents or active metabolic release. Immunoglobulins were identified and isolated by immunological coprecipitation. The polypeptide chain structure of immunoglobulins isolated from lymphocyte surfaces was analyzed by polyacrylamide gel electrophoresis of reduced, alkylated samples in acid urea. Human and murine thymus lymphocytes possessed only IgM immunoglobulin on their surfaces. This protein contained light chains and micro-type heavy chains and was characterized by a molecular weight of approximately 200,000. Murine splenic lymphocytes from CBA x C57 animals and congenitally athymic (nu/nu) mice possessed both IgM and IgG on their surfaces. The ratio of micro-chain to gamma-chain was about 3/1. The presence of IgM on thymus lymphocytes probably does not reflect trace contamination by B lymphocytes because comparable quantities of IgM were isolated from both cell populations. Metabolic turnover data suggest that this immunoglobulin is synthesized by the cell population studied. These results provide direct evidence for the presence of immunoglobulins composed of light and heavy polypeptide chains on the surfaces of lymphocytes of all classes.
免疫球蛋白是从多种淋巴细胞群体的淋巴细胞表面分离得到的,这些群体包括小鼠和人类胸腺淋巴细胞以及小鼠脾脏和胸导管淋巴细胞。细胞表面蛋白通过乳过氧化物酶催化碘化用碘(125I)进行标记,然后通过在解离溶剂中溶解或通过活跃的代谢释放回收至溶液中。免疫球蛋白通过免疫共沉淀进行鉴定和分离。从淋巴细胞表面分离得到的免疫球蛋白的多肽链结构,通过在酸性尿素中对还原、烷基化样品进行聚丙烯酰胺凝胶电泳进行分析。人类和小鼠胸腺淋巴细胞表面仅具有IgM免疫球蛋白。该蛋白包含轻链和微型重链,其特征在于分子量约为200,000。来自CBA×C57动物和先天性无胸腺(nu/nu)小鼠的小鼠脾脏淋巴细胞表面同时具有IgM和IgG。微型链与γ链的比例约为3/1。胸腺淋巴细胞上IgM的存在可能并不反映B淋巴细胞的微量污染,因为从这两种细胞群体中分离得到的IgM量相当。代谢周转数据表明,这种免疫球蛋白是由所研究的细胞群体合成的。这些结果为所有类型淋巴细胞表面存在由轻链和重链多肽组成的免疫球蛋白提供了直接证据。