Inada K, Okada S, Phuchareon J, Hatano M, Sugimoto T, Moriya H, Tokuhisa T
Department of Developmental Genetics, Chiba University Graduate School of Medicine, Japan.
J Immunol. 1998 Oct 15;161(8):3853-61.
We examined the role of c-Fos in the differentiation of mature B cells into IgG-producing cells using transgenic mice carrying the c-fos gene under the control of the IFN-alpha/beta-inducible Mx promoter (Mx-c-fos) or the constitutive H-2Kb promoter (H2-c-fos). Splenic B cells from Mx-c-fos mice were cultured with LPS and rIL-4, and IgG1+ B cells were developed in the culture after day 3. When IFN-alpha/beta was added to the culture from day 2, development of IgG1+ B cells was perturbed, and the number of apoptotic cells increased within 24 h, suggesting that c-Fos induces apoptosis in Ig class-switching B cells. To confirm the effect of c-Fos on B cell differentiation in vivo, H2-c-fos mice were immunized with DNP-OVA. The mice produced primary IgM, but not IgG, anti-DNP Ab in serum and failed to generate germinal centers in spleen. The perturbation of germinal center formation in H2-c-fos mice was rescued by mating them with transgenic mice carrying the bcl-2 gene with the Ig promoter. However, primary IgG1 anti-DNP Ab production was still suppressed in doubly transgenic mice, suggesting that Bcl-2 can delay the time of c-Fos-induced apoptosis in Ig class-switching B cells but cannot rescue the death. Since c-Fos is induced in mature B cells reacted with Ags, and clonal deletion of self-reactive B cells in germinal centers is insensitive to Bcl-2, these results suggest that c-Fos plays a causal role in clonal deletion of germinal center B cells.
我们利用在干扰素α/β诱导型Mx启动子（Mx-c-fos）或组成型H-2Kb启动子（H2-c-fos）控制下携带c-fos基因的转基因小鼠，研究了c-Fos在成熟B细胞分化为产生IgG的细胞过程中的作用。将来自Mx-c-fos小鼠的脾B细胞与LPS和rIL-4一起培养，3天后培养物中出现了IgG1+B细胞。从第2天开始向培养物中添加干扰素α/β时，IgG1+B细胞的发育受到干扰，24小时内凋亡细胞数量增加，这表明c-Fos在Ig类别转换B细胞中诱导凋亡。为了证实c-Fos在体内对B细胞分化的影响，用DNP-OVA免疫H2-c-fos小鼠。这些小鼠血清中产生了初级IgM抗DNP抗体，但没有产生IgG抗DNP抗体，并且脾脏中未能形成生发中心。通过将H2-c-fos小鼠与携带带有Ig启动子的bcl-2基因的转基因小鼠交配，挽救了H2-c-fos小鼠中生发中心形成的干扰。然而，双转基因小鼠中初级IgG1抗DNP抗体的产生仍然受到抑制，这表明Bcl-2可以延迟c-Fos在Ig类别转换B细胞中诱导的凋亡时间，但不能挽救细胞死亡。由于c-Fos在与抗原反应的成熟B细胞中被诱导，并且生发中心中自身反应性B细胞的克隆缺失对Bcl-2不敏感，这些结果表明c-Fos在生发中心B细胞的克隆缺失中起因果作用。
