Introduction

Type 1 Diabetes is a significant barrier to islet transplant as grafts are subject to both alloimmunity and recurrent autoimmunity. No better is this clinical scenario modeled than the T1D-prone non-obese diabetic (NOD) mouse, a model in which no therapy has ever induced permanent transplant tolerance to islet allografts or any other allograft, indicating the severity of the immunologic barrier. As B lymphocytes play a critical role in T1D, we hypothesized that eliminating B lymphocytes would enhance tolerance induction.

Methods

Diabetic NOD mice and B cell deficient NOD mice (NODuMT) were transplanted with C3H islets and tolerized with 100ug anti-CD45RB on days 0,1,3,5,7 or left untreated. Rejection was determined by two consecutive BG readings > 250mg/dL. To confirm the tolerant state, grafted islets were removed and return to hyperglycemia noted. Hyperglycemic recipients were then retransplanted with matched C3H islet allografts, received no further treatment, and the maintenance of euglycemia monitored. Tolerant grafts were analyzed via IHC and lymphocyte populations were evaluated by flow cytometry.

Results

B lymphocyte deficient NODuMT mice were susceptible to tolerance induction in almost 100% of recipients. Removal of the graft resulted in recurrent hyperglycemia (confirming graft function) and retransplant of a matched graft was accepted without further treatment. Immunohistochemical analyses of tolerant islet allografts demonstrated significant infiltration of protective CD4 T Regulatory Cells (CD4 Tregs), whose expansion was restrained by B lymphocytes. Furthermore, we observed a significant expansion of Vbeta3+ CD4 Tregs in NODuMT mice, a clonotypic T cell population which when expanded, confers protection from T1D. Our investigation demonstrated direct B cell-Treg interactions by imaging cytometry and suggest that thymic resident B cells may negatively select Tregs in NOD mice.

Conclusions

These discoveries 1) represent the first instance in which permanent transplant tolerance has been achieved in NOD mice and 2) highlight the deleterious role that B lymphocytes play in the establishment of transplant tolerance in T1D.

CITATION INFORMATION: Stocks B, Wilson C, Meehan D, Marshall A, Moore D. B Lymphocytes Prevent Transplantation Tolerance in NOD Mice by Limiting CD4 Treg Function. Am J Transplant. 2016;16 (suppl 3).

« Back to 2016 American Transplant Congress