PDF(Pubmed)
Abstract：
Camelids produce both conventional tetrameric antibodies (Abs) and dimeric heavy-chain antibodies (HCAbs). Although B cells that generate these two types of Abs exhibit distinct B cell receptors (BCRs), whether these two B cell populations differ in their phenotypes and developmental processes remains unclear. Here, we performed single-cell 5\' RNA profiling of peripheral blood mononuclear cell samples from Bactrian camels before and after immunization. We characterized the functional subtypes and differentiation trajectories of circulating B cells in camels, and reconstructed single-cell BCR sequences. We found that in contrast to humans, the proportion of T-bet+ B cells was high among camelid peripheral B cells. Several marker genes of human B cell subtypes, including CD27 and IGHD, were expressed at low levels in the corresponding camel B cell subtypes. Camelid B cells expressing variable genes of HACbs (VHH) were widely present in various functional subtypes and showed highly overlapping differentiation trajectories with B cells expressing variable genes of conventional Abs (VH). After immunization, the transcriptional changes in VHH+ and VH+ B cells were largely consistent. Through structure modeling, we identified a variety of scaffold types among the reconstructed VHH sequences. Our study provides insights into the cellular context of HCAb production in camels and lays the foundation for developing single-B cell-based camelid single-domain Ab screening.
摘要：
骆驼科动物产生常规四聚体抗体(Ab)和二聚体重链抗体(HCAb)。尽管产生这两种Abs的B细胞表现出不同的B细胞受体（BCR），这两种B细胞群的表型和发育过程是否不同尚不清楚.这里,我们在免疫前后对双峰骆驼外周血单个核细胞样本进行了单细胞5'RNA分析.我们表征了骆驼循环B细胞的功能亚型和分化轨迹，和重建的单细胞BCR序列。我们发现与人类相比，骆驼外周血B细胞中T-bet+B细胞比例较高。人类B细胞亚型的几个标记基因,包括CD27和IGHD,在相应的骆驼B细胞亚型中以低水平表达。表达HACbs（VHH）可变基因的骆驼B细胞广泛存在于各种功能亚型中，并显示出与表达常规Ab（VH）可变基因的B细胞高度重叠的分化轨迹。免疫接种后,VHH+和VH+B细胞的转录变化基本一致。通过结构建模,我们在重建的VHH序列中鉴定了多种支架类型.我们的研究提供了有关骆驼HCAb产生的细胞背景的见解，并为开发基于单B细胞的骆驼单域Ab筛选奠定了基础。
