Kupfer H, Monks C R, Kupfer A
Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
J Exp Med. 1994 May 1;179(5):1507-15. doi: 10.1084/jem.179.5.1507.
Antigen (Ag)-specific T helper (Th) cells regulate the proliferation and differentiation of Ag-specific B cells by secreting cytokines and by expressing activating receptors like gp39. In vitro, the cytokines and the activating receptors function in an Ag-nonspecific manner. It is unclear, therefore, how Ag specificity is imposed on B cell responses in physiological Th-B cell interactions. Here we studied, at the single cell level, the interactions between cloned Th cells and small splenic B cells, which served as Ag-specific antigen-presenting cells (APCs) to the Th cells. Digital confocal immunofluorescence microscopy of Th-B cell conjugates revealed significant variability in the molecular and cellular properties of these interactions, in spite of the fact that all the interactions in this system were expected to be Ag specific. After 30 h of incubation B cells began to divide, and this process was entirely dependent on the presence of both Th cells and Ag. Immunofluorescence microscopic studies showed that essentially all the mitotic B cells were bound to Th cells and faced the microtubule organizing center (MTOC) in the Th cells where interleukin 4 was highly concentrated. Other B cells that were bound to the same Th cells but were not close to the Th-MTOC remained in interphase. These results provide the first direct structural and functional evidence that the site of interaction of B cells with Th cells affects their immune response. We propose that, during Ag-induced Th-B cell interactions, B cells that are bound facing the Th-MTOC proliferate preferentially because they are the recipients of locally secreted cytokines. In addition, these B cells may interact with newly expressed receptors, which may also be locally inserted into the Th membrane. The polarized delivery of activating molecules towards the Th-bound APCs may impose functional specificity on effector molecules that otherwise are not Ag specific.
抗原（Ag）特异性辅助性T（Th）细胞通过分泌细胞因子和表达如gp39等激活受体来调节Ag特异性B细胞的增殖和分化。在体外，细胞因子和激活受体以Ag非特异性方式发挥作用。因此，尚不清楚在生理性Th-B细胞相互作用中Ag特异性是如何赋予B细胞应答的。在此，我们在单细胞水平上研究了克隆的Th细胞与小的脾B细胞之间的相互作用，小的脾B细胞作为Th细胞的Ag特异性抗原呈递细胞（APC）。Th-B细胞结合物的数字共聚焦免疫荧光显微镜检查显示，尽管该系统中的所有相互作用都预期是Ag特异性的，但这些相互作用的分子和细胞特性存在显著差异。孵育30小时后，B细胞开始分裂，并且这个过程完全依赖于Th细胞和Ag的存在。免疫荧光显微镜研究表明，基本上所有有丝分裂的B细胞都与Th细胞结合，并面向Th细胞中白细胞介素4高度浓缩的微管组织中心（MTOC）。其他与相同Th细胞结合但不靠近Th-MTOC的B细胞则停留在间期。这些结果提供了首个直接的结构和功能证据，表明B细胞与Th细胞的相互作用位点会影响其免疫应答。我们提出，在Ag诱导的Th-B细胞相互作用过程中，面向Th-MTOC结合的B细胞优先增殖，因为它们是局部分泌细胞因子的接受者。此外，这些B细胞可能与新表达的受体相互作用，这些受体也可能局部插入到Th细胞膜中。激活分子向与Th结合的APC的极化递送可能赋予效应分子功能特异性，否则这些效应分子不是Ag特异性的。
