Control mechanisms for B cell apoptosis and differentiation

我们已经评估了T细胞和滤泡树突状细胞对B细胞凋亡和分化的调节机制。为此目的，我们首先建立了细胞系统，其中衬里的B细胞的凋亡由衬里的T细胞或FDC或来自这些细胞的限定分子调节。事实上，无论是内衬的FDC还是表达CD 40 L的T细胞都能拯救B细胞系WEHI-231免于抗原受体介导的凋亡。由于FDC细胞不表达CD 40配体，FDC可能通过不依赖CD 40的机制拯救WEHI-231细胞。此外，CD 40信号而不是FDC诱导抗凋亡分子Bcl-2和Bcl-x的表达，表明FDC通过与CD 40信号不同的机制拯救WEHI-231细胞。在其他研究中，我们发现，<Kip1>在WEHI-231中，负调节细胞周期进程的细胞周期蛋白依赖性激酶抑制剂p27 α通过抗原受体信号传导上调，并通过CD 40信号传导下调。我们将WEHI-231培养于 ...更多信息 在p27 ~+反义寡核苷酸的存在<Kip1>下，WEHI-231在抗原受体交联后不能发生凋亡，这表明p27 ~+<Kip1>是B细胞存活的CD 40信号传导的重要靶分子。我们建立了CH 12 B淋巴瘤细胞的亚克隆（F3），其在CD 40配体、IL-4和TGF-β存在下有效地经历从IgM到伊加的类别转换。在这些细胞中，免疫球蛋白C区的去甲基化而非种系转录与类别转换的效率相关。这一结果表明，去甲基化，而不是生殖细胞系转录可能在类转换中发挥作用。为了鉴定参与类别转换的分子，我们分离了在用CD 40配体、IL-4和TGF-β处理的F3细胞中特异性表达的两个基因。这些基因的功能有待确定。少

We have assessed the regulatory mechanisms for B cell apoptosis and differentiation by T cells and follicular dendritic cells. For this purpose, we first established the cellular systems in which apoptosis of lined B cells is regulated by lined T cells or FDC,or defined molecules derived from these cells. Indeed, the B cell line WEHI-231 was rescued from antigen receptor-mediated apoptosis by either lined FDC or T cells expressing CD40L.Since FDC cells did not express ligands for CD40, FDC may rescue WEHI-231 cells by CD40-independent mechanisms. Moreover, CD40 signaling but not FDC induced expression of anti-apoptotic molecules, Bcl-2 and Bcl-x, suggesting that FDC rescues WEHI-231 cells by distinct mechanisms from CD40 signaling. In other studies, we found that the cyclin-dependent kinase inhibitor p27^<Kip1>, which negatively regulate cell cycle progression, is upregulated by antigen receptor signaling and down modulated by CD40 signaling in WEHI-231. When we cultured WEHI-231 in th … More e presence of the antisense oligonucleotides for p27^<Kip1>, WEHI-231 failed to undergo apoptosis upon antigen receptor crosslinking, suggesting that p27^<Kip1> is an important target molecule of CD40 signaling for B cell survival.We also established the cellular system in which molecular mechanisms for immunoglobulin class switching, a crucial step of B cell differentiation, can be assessed. We established a subclone (F3) of CH12 B lymphoma cells which undergo class switching frm IgM to IgA efficiently in the presence of CD40 ligand, IL-4 and TGF-beta. In these cells, Demethylation but not germline transcription of the C region of the immunoglobulin correlates to the efficiency of class switching. This result suggests that demethylation but not germ line transcription may play a role in class switching. To identify the molecules involved in class switching, we isolated two genes specifically expressed in F3 cells treated with CD40 ligand, IL-4 and TGF-beta. Functions of these genes are to be determined. Less