George A, Cebra J J
Department of Biology, University of Pennsylvania, Philadelphia 19104-6018.
Proc Natl Acad Sci U S A. 1991 Jan 1;88(1):11-5. doi: 10.1073/pnas.88.1.11.
B cells purified from the germinal centers (GCs) of murine Peyer's patches can be stimulated in a clonal microculture containing helper T cells and dendritic cells to divide and secrete immunoglobulin. Intraclonal isotype switching occurs, and a variety of immunoglobulin isotypes, including IgA, is secreted. Memory cells, which generate clones secreting IgA exclusively, are only rarely identified in the GC B-cell subset. Such memory cells can, however, be readily identified among unfractionated Peyer's patch B cells, and in non-GC subsets of B cells. The results suggest that the GC does not contain IgA memory cells that can be restimulated in vitro to secrete only IgA. When division of GC B cells is prevented by irradiation or aphidicholin treatment, a large subset that secretes IgA as the sole immunoglobulin isotype is seen, and the output of presumably single B cells is large enough to be scored by RIA. Both helper T cells and dendritic cells are required for the phenomenon. The data indicate that commitment to IgA secretion occurs in Peyer's patch GCs and suggest that the prolific cell division known to be supported in GCs may forestall terminal differentiation of preplasmablasts to immunoglobulin secretion.
从小鼠派尔集合淋巴结生发中心（GCs）纯化的B细胞，可在含有辅助性T细胞和树突状细胞的克隆微培养体系中受到刺激而发生分裂并分泌免疫球蛋白。克隆内会发生同种型转换，并分泌包括IgA在内的多种免疫球蛋白同种型。在GC B细胞亚群中，仅分泌IgA的克隆所产生的记忆细胞很少见。然而，这类记忆细胞在未分离的派尔集合淋巴结B细胞以及B细胞的非GC亚群中很容易被识别。结果表明，GC中不存在能在体外再次刺激后仅分泌IgA的IgA记忆细胞。当通过照射或阿非迪霉素处理阻止GC B细胞分裂时，会出现一个以分泌IgA作为唯一免疫球蛋白同种型的大的亚群，而且推测单一B细胞的分泌量足以通过放射免疫分析（RIA）进行测定。该现象需要辅助性T细胞和树突状细胞两者的参与。这些数据表明，派尔集合淋巴结GCs中会发生向IgA分泌的定向分化，并且提示已知在GCs中得到支持的大量细胞分裂可能会阻止前浆细胞向免疫球蛋白分泌的终末分化。
