Strober S
J Immunol. 1975 Feb;114(2 pt 2):877-85.
Thoracic duct and spleen cells of normal (unimmunized) adult rats were fractionated according to size by 1 times G velocity sedimentation. Fractions were tested for their ability to restore the adoptive antibody response of irradiated hosts to horse spleen ferritin. A constant source of T cells (small numbers of unfractionated thoracic duct cells) was added to each fraction in order to monitor the B cell activity of the latter. Although large and small cell fractions of the spleen showed restorative activity, only the small cell fractions of the thoracic duct lymph showed activity. The turnover rate of the spleen cell fractions was determined by treating donors with high specific-activity 3H-thymidine for 48 hr before splenectomy. Rapidly dividing cells are preferentially killed by this treatment. The results suggest that a considerable proportion of large, intermediate, and small virgin B cells turn over within 48 hr. The cell surface of the various spleen cell fractions was examined for the presence of immunoglobulin (Ig) and a receptor for complement. The percentage of Ig-bearing cells in the large cell fractions was similar to the percentage of cells bearing IgM and a receptor for complement. However, the majority of Ig-bearing cells in the small cell fractions did not show the latter two surface markers. Experiments with the fluorescence-activated cell sorter showed that the large functionally active B cells bore surface IgM. The experimental findings suggest that there are subpopulations of virgin B cells in the spleen of the adult rat which differ with respect to size, migration pattern, turnover rate, and cell surface characteristics. The relationship of these cells to one another is discussed in the framework of an antigen-independent model of B cell maturation in the rat.
将正常（未免疫）成年大鼠的胸导管和脾细胞按1倍重力沉降速度根据大小进行分级分离。检测各分级分离物恢复受照射宿主对马脾铁蛋白的过继性抗体反应的能力。为监测各分级分离物的B细胞活性，向每个分级分离物中添加恒定来源的T细胞（少量未分级的胸导管细胞）。尽管脾的大细胞分级分离物和小细胞分级分离物均显示出恢复活性，但只有胸导管淋巴的小细胞分级分离物显示出活性。通过在脾切除术前用高比活性的³H-胸腺嘧啶处理供体48小时来测定脾细胞分级分离物的周转率。这种处理优先杀死快速分裂的细胞。结果表明，相当比例的大、中、小未成熟B细胞在48小时内更新。检查各种脾细胞分级分离物的细胞表面是否存在免疫球蛋白（Ig）和补体受体。大细胞分级分离物中携带Ig的细胞百分比与携带IgM和补体受体的细胞百分比相似。然而，小细胞分级分离物中大多数携带Ig的细胞未显示后两种表面标志物。用荧光激活细胞分选仪进行的实验表明，功能活跃的大B细胞带有表面IgM。实验结果表明，成年大鼠脾中存在未成熟B细胞亚群，它们在大小、迁移模式、周转率和细胞表面特征方面存在差异。在大鼠B细胞成熟的抗原非依赖性模型框架内讨论了这些细胞之间的关系。
