Arakawa Hiroshi, Kuma Kei-ichi, Yasuda Masahiro, Ekino Shigeo, Shimizu Akira, Yamagishi Hideo
Department of Biophysics, Graduate School of Science, Center for Molecular Biology and Genetics, Kyoto University, Japan.
J Immunol. 2002 Jul 15;169(2):818-28. doi: 10.4049/jimmunol.169.2.818.
In chickens, a single set of unique functional segments of both Ig H and L chain genes is rearranged during early embryogenesis to generate a pool of B cell progenitors that will be diversified in the bursa by gene conversion, forming the preimmune repertoire. After hatching, bursal cells are exposed to environmental Ags in the bursal lumen. We prepared B cells from each single bursal follicle and used PCR-directed Ig L chain gene analysis to study the differentiation of B cells and the effect of antigenic stimulation from the bursal lumen on the neonatal chicken B cell repertoire formation. Selective amplification of B cell clones with a productive V-J joint was observed during the late embryonic stage, possibly by the interaction with ligands expressed on the bursal stroma and further accelerated in the neonatal chicken. Administration of the artificial Ags into the bursal lumen before the isolation of bursa by bursal duct ligation in the embryo caused a significant increase in lymphocytes with a productive V-J joint in the neonatal chicken bursa compared with the isolated bursa. Intra- and interclonal diversity of a complementarity-determining region measured by an evolutionary distance increased during bursal development. Clonal diversification did not require stimulation by artificial Ags from the bursal lumen. Thus, the preimmune repertoire in the bursa is generated by gene conversion during Ag-independent B cell proliferation, and antigenic stimulation from the bursal epithelium to bursal B cells plays roles in the selection of clones with a productive V-J joint.
在鸡中，Ig重链和轻链基因的一组独特功能片段在胚胎发育早期重排，以产生一群B细胞祖细胞，这些祖细胞将在法氏囊中通过基因转换实现多样化，从而形成免疫前库。孵化后，法氏囊细胞在法氏囊腔中接触环境抗原。我们从每个单独的法氏囊滤泡中制备B细胞，并使用聚合酶链反应（PCR）指导的Ig轻链基因分析来研究B细胞的分化以及法氏囊腔中抗原刺激对新生鸡B细胞库形成的影响。在胚胎后期观察到具有有效V-J连接的B细胞克隆的选择性扩增，这可能是通过与法氏囊基质上表达的配体相互作用实现的，并且在新生鸡中进一步加速。在胚胎期通过法氏囊导管结扎分离法氏囊之前，向法氏囊腔中注入人工抗原，与分离的法氏囊相比，导致新生鸡法氏囊中具有有效V-J连接的淋巴细胞显著增加。在法氏囊发育过程中，通过进化距离测量的互补决定区的克隆内和克隆间多样性增加。克隆多样化不需要法氏囊腔中的人工抗原刺激。因此，法氏囊中的免疫前库是在不依赖抗原的B细胞增殖过程中通过基因转换产生的，并且法氏囊上皮对法氏囊B细胞的抗原刺激在选择具有有效V-J连接的克隆中发挥作用。
