Single-cell 5' RNA sequencing of Bactrian camel PBMCs

Camelids are capable of producing both conventional tetrameric antibodies (Abs) and dimeric heavy-chain antibodies (HCAbs). While B cells generating these two types of Abs exhibit distinct B-cell receptors (BCRs), it remains unclear whether these two B cell populations differ in their phenotypes and developmental processes. Here, we collected eight PBMC samples before and after immunization from four Bactrian camels and conducted single-cell 5’ RNA sequencing. We characterized the functional subtypes and differentiation trajectories of circulating B cells in camels, including native B cells, memory B cells, intermediate B cells, atypical B cells, and plasma cells. Additionally, we reconstructed single-cell BCR sequences and revealed the IGHV and IGHC gene types. We found that B cells with variable genes of HACbs (VHH) were widely present in various functional subtypes and showed highly overlapping differentiation trajectories to B cells with variable genes of conventional Abs (VH). After immunization, the transcriptional changes in VHH+ and VH+ B cells were also largely consistent. Our study not only elucidates the cellular context of HCAb production in camels, but also lays the foundation for the development of single B cell-based nanobody screening. We conducted single-cell 5' RNA sequencing on PBMCs from four adult healthy camels (C1-C4) from Inner Mongolia. Additionally, two camels (C3, C4) were immunized with BSA as an antigen, and PBMCs were collected at two time points after four immunizations (42 days and 56 days) for single-cell 5' RNA sequencing. We identified cell types in camel PBMCs, focusing on B cell subtypes and differentiation trajectories. Furthermore, we reconstructed single-cell BCR sequences and investigated the associations between B cell phenotypes and BCR types.