Studies on the B cell development and its microenvironment

我们对胸腺中的B细胞祖细胞进行了表征。成熟胸腺B细胞为sIg^+、B220^+、CD43^-，胸腺B细胞祖细胞为sIg^-、B220^<med>、CD43^+。从B细胞祖细胞中提取的DNA经PCR扩增、印迹和探针检测后，大多数祖细胞显示出重排的Ig D-J和V-D-J模式。当从胸腺中纯化出B细胞祖细胞，并将其注入胸腺内的不同受体中，在胸腺中检测到携带供体型Igh6的B细胞，但在周围没有检测到。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，从胸腺纯化的B细胞接种B细胞祖细胞后，在CD40配体和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等位型的IgM。经静脉注射胸腺祖B细胞后，胸腺祖B细胞可分化为成熟的B细胞，注射后胸腺中CD5^+ B细胞的比例明显高于脾脏和淋巴结。这些发现提示B细胞的表面表型可能受到微环境的影响。阐明支持胸腺祖B细胞、基质细胞分化的体外条件。在IL-7存在的情况下，胸腺基质细胞支持胸腺祖B细胞的分化，而骨髓基质细胞和胸腺细胞系不支持。

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.