*Purpose: Tim1 signaling has an important role in inducing and maintaining the function of Regulatory B cells. Our previous study showed that Tim1+ Bregs prolong the survival of islets in an allotransplantation model (Balb/c to C57BL/6). Here we examined the potential pathways and Breg subsets underlying TIM1+ Breg mediated regulation by RNA-seq and single-cell RNA-sequencing (scRNA-seq) analysis.

*Methods: 30M Balb/c irradiated splenocytes were injected intraperitoneally into C57BL/6 recipients. After 14 days, Tim1- and Tim1+ cells were isolated for 10X Genomics 3’ scRNA-seq analysis. The data was analyzed using Cell Ranger (version 3.1.0) and R programming (version: 3.6.3).

*Results: Clustering of transcriptionally similar cells identified eight clusters of Tim1+ and Tim1- B cells (Figure 1a). The annotation results showed that Tim1- B cells were mainly included in cluster 0 (Klf2hiIglc1lo B cells), cluster 1 (Klf2hiIglc1hi B cells), and cluster 5 (Ifit3+ B cells). Immunology-relevant pathways were positively enriched in both clusters 0 and 5, suggesting that those cell populations were the main effector clusters of Tim1-B cells, potentially promoting allograft rejection (Figure 1b). Tim1+B cells were mainly included in cluster 2 (Klf2+Mifhi B cells), cluster 3 (Klf2+Cd21hi B cells), cluster 4 (Stmn1+Tim1+ Bregs), and cluster 6 (Cd106+Tim1+ B cells). Pathway enrichment analysis indicated that clusters 2 and 4 had similar enriched pathways, suggesting that clusters 2 and 4 were the primary immunosuppressive subset of Tim1+ Bregs (Figure). Cluster 7, mainly from Tim1+ Bregs, were identified as the plasma cells.

*Conclusions: Subsets of Tim1+ and Tim1- B cells differ vastly in their gene expression, correlating with their roles during allogeneic transplantation. The ongoing analysis may illuminate key pathways that regulate the function of Klf2+Mifhi B cells and Stmn1+Tim1+ Bregs.

« Back to 2021 American Transplant Congress