Studies on the B cell development and its microenvironment

我们描述了胸腺中 B 细胞祖细胞的特征。虽然成熟胸腺B细胞是sIg^、B220^，但胸腺中的CD43^-、B细胞祖细胞是sIg^-、B220^<med>和CD43^。当分选的 B 细胞祖细胞的 DNA 通过 PCR 扩增、印迹和探测时，大多数祖细胞显示出重排的 Ig D-J 和 V-D-J 模式。当从胸腺中纯化 B 细胞祖细胞并通过胸腺内注射到不同的 Igh 同种异型受体中时，在胸腺中检测到了携带供体型 Igh6 的 B 细胞，但在外周却没有检测到。由这些祖细胞产生的胸腺B细胞是CD5^细胞，尽管CD5分子的表达范围很广。此外，从接种B细胞祖细胞的胸腺中纯化的B细胞在CD40配体加IL-10的影响下能够分化为抗体形成细胞，并分泌具有供体Igh6同种异型的IgM。当胸腺祖B细胞静脉注射给scid小鼠时，胸腺祖B细胞可以分化为成熟B细胞，静脉注射后检测到胸腺中CD5^B细胞的百分比。注射量明显高于脾脏和淋巴结。这些发现表明 B 细胞的表面表型可能受到微环境的影响。阐明支持胸腺 B 祖细胞、基质细胞分化的体外条件。在 IL-7 存在的情况下，胸腺基质细胞（但不是来自骨髓的基质细胞或胸腺细胞系）可以支持胸腺祖 B 细胞的分化。

We characterize B cell progenitors in the thymus. Though mature thymic B cells are sIg^+, B220^+, but CD43^-, B cell progenitors in the thymus were found to be sIg^-, B220^<med>, and CD43^+. Most progenitors showed rearranged Ig D-J and V-D-J patterns when DNA from sorted B cell progenitors was amplified by PCR,blotted and probed. When B cell progenitors were purified from the thymus and injected intrathymically into Igh-allotype disparate recipients, B cells bearing donor-type Igh6 were detected in the thymus but not in the periphery. Thymic B cells generated from these progenitors were CD5^+ cells, though there was a broad range of expression of CD5 molecules. Furthermore, B cells purified from thymus that had been inoculated with B cell progenitors were able to differentiate into antibody-forming cells under the influence of CD40 ligand plus IL-10, and secreted IgM with donor Igh6-allotype. When thymic progenitor B cells were intravenously injected into scid mice, thymic progenitor B cells can differentiate to mature B cells, and the percentage of CD5^+ B cells detected in the thymus after iv. injection was significantly higher than those in the spleen and lymph nodes. These findings indicate the possibility that the surface phenotye of B cells is influenced by the microenvironment. To clarify the in vitro condition that supports the differentiation of thymic progenitor B cells, stroma cells. In the presence of IL-7, thymic stroma cells, but not stroma cells from the bone marrow nor thymic cell lines, could support the differentiation of thymic progenitor B cells.