Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada;
J Immunol. 2014 Apr 1;192(7):3207-17. doi: 10.4049/jimmunol.1302394. Epub 2014 Feb 10.
Although the negative selection of self-reactive B cells in the bone marrow of mammals has been clearly demonstrated, it remains unclear in models of gut-associated B cell lymphopoiesis, such as that of the chicken (Gallus gallus). We have generated chicken surface IgM-related receptors in which the diversity region of the lamprey variable lymphocyte receptor (VLR) has been fused to the C region of chicken surface IgM (Tμ). Expression of a VLR:Tμ receptor with specificity for PE supported normal development of B cells, whereas a VLR:Tμ receptor specific to hen egg lysozyme (a self-antigen with respect to chicken B cells) induced, in vivo, complete deletion of VLR(HEL)Tμ-expressing B cells. In ovo i.v. injection of PE resulted in deletion of VLR(PE)Tμ-expressing Β cells in the embryo spleen, demonstrating that negative selection was independent of the bursal microenvironment. Although chickens transduced with a murine CD8α:chicken Igα fusion protein contained B cells expressing mCD8α:chIgα, cotransfection of the mCD8α:chIgα construct, together with thymus leukemia Ag (a natural ligand for mCD8α), resulted in reduced levels of mCD8α:chIgα-expressing B cells in inverse proportion to the levels of thymus leukemia Ag-expressing cells. Deletion of mCD8α:chIgα-expressing cells was specific for B cells and required active signaling downstream of the mCD8α:chIgα receptor. Ag-mediated negative selection of developing chicken B cells can therefore occur independently of the bursal microenvironment and is dependent on signaling downstream of the BCR.
尽管哺乳动物骨髓中自身反应性 B 细胞的阴性选择已得到明确证实，但在肠道相关 B 细胞淋巴发生的模型中，如鸡（Gallus gallus）中，情况尚不清楚。我们已经生成了鸡表面 IgM 相关受体，其中七鳃鳗可变淋巴细胞受体（VLR）的多样性区与鸡表面 IgM（Tμ）的 C 区融合。表达针对 PE 的 VLR:Tμ 受体特异性支持 B 细胞的正常发育，而针对鸡卵溶菌酶（相对于鸡 B 细胞的自身抗原）的 VLR:Tμ 受体特异性则导致体内表达 VLR（HEL）Tμ 的 B 细胞完全删除。在鸡胚中静脉内注射 PE 导致胚胎脾脏中表达 VLR（PE）Tμ 的 Β 细胞被删除，证明阴性选择不依赖于法氏囊微环境。尽管转导了小鼠 CD8α：鸡 Igα 融合蛋白的鸡含有表达 mCD8α：chIgα 的 B 细胞，但共转染 mCD8α：chIgα 构建体以及胸苷白血病 Ag（mCD8α 的天然配体）导致 mCD8α：chIgα 表达的 B 细胞水平降低与胸苷白血病 Ag 表达细胞的水平成反比。mCD8α：chIgα 表达细胞的删除特异性针对 B 细胞，并且需要 mCD8α：chIgα 受体下游的活性信号。因此，发育中的鸡 B 细胞的 Ag 介导的阴性选择可以独立于法氏囊微环境发生，并且依赖于 BCR 下游的信号。
