Identification of the Subsets of IL-10-Producing Regulatory B Cells in the Course of Tolerance Induction and Maintenance in Islet Allotransplantation.

Background: Our previous study demonstrated that regulatory B cells (Bregs) play an indispensable role in dual anti-CD45RB/anti-TIM-1 antibody-induced transplantation tolerance through an IL-10-dependent pathway. However, the potentially specific subsets of Bregs have not been clearly demonstrated. In this study, we aimed to detect the subsets of the Bregs possessing the ability to produce IL-10 in the early stage and tolerance maintenance stage of allogeneic islet transplantation treated by dual anti-CD45RB/anti-TIM-1.

Methods: Isolated Balb/C islets were transplanted under the kidney capsule of C57BL/6J diabetic mice. The recipients were treated with anti-CD45RB and anti-TIM-1. Two major IL-10-producing Breg subsets of CD19CD5CD1d B10 cells and CD19TIM-1B cells, and the T cells of CD4CD25 (Tregs), CD4IFN-γ Th1 cells, and CD4IL-4 Th2 cells in splenocytes of grafted recipients were detected by flow cytometry after 1 week, 2 weeks, and more than 100 days posttransplantation.

Results: On day 14 after islet transplantation, the frequency of CD19CD5CD1d B10 cells in recipient mice increased significantly, compared with day 0 and 7 (P = .001, P < .001, respectively), while it dropped to normal level in the recipients with long-term graft survival. In contrast, there was significant increase of CD19TIM-1B cells on day 14 (P = .003) and day 100 after transplant (P = .009). CD4CD25 Treg cells have similar increasing tendency with CD19TIM-1B cells, as they increased from normal 10% to almost 20% both on day 14 and day 90 after transplantation. Conversely, the expression of CD4IFN-γ Th1 cells decreased significantly on day 14 (P = .004) and on day 100 after transplant (P = .002). As another kind of helper T cells, CD4IL-4 Th2 cells increased only on day 14 after transplant (P < .001).

Conclusions: CD19CD5CD1d B10 cells may play an important role only in the early stage of transplantation tolerance induction by dual anti-CD45RB/anti-TIM-1 antibody treatment, whereas CD19TIM-1B cells may play crucial parts in the whole process of tolerance induction and maintenance.