Low-Dose Interleukin-2 Combined With Rapamycin Led to an Expansion of CD4+CD25+FOXP3+ Regulatory T Cells and Prolonged Human Islet Allograft Survival in Humanized Mice

Abstract

Islet transplantation is an emerging therapy for type 1 diabetes and hypoglycemic unawareness. However, a key challenge for islet transplantation is cellular rejection and the requirement for long-term immunosuppression. In this study, we established a diabetic humanized NOD-scidIL2Rγnull (NSG) mouse model of T-cell–mediated human islet allograft rejection and developed a therapeutic regimen of low-dose recombinant human interleukin-2 (IL-2) combined with low-dose rapamycin to prolong graft survival. NSG mice that had received renal subcapsular human islet allografts and were transfused with 1 × 107 of human spleen mononuclear cells reconstituted human CD45+ cells that were predominantly CD3+ T cells and rejected their grafts with a median survival time of 27 days. IL-2 alone (0.3 × 106 IU/m2 or 1 × 106 IU/m2) or rapamycin alone (0.5–1 mg/kg) for 3 weeks did not prolong survival. However, the combination of rapamycin with IL-2 for 3 weeks significantly prolonged human islet allograft survival. Graft survival was associated with expansion of CD4+CD25+FOXP3+ regulatory T cells (Tregs) and enhanced transforming growth factor-β production by CD4+ T cells. CD8+ T cells showed reduced interferon-γ production and reduced expression of perforin-1. The combination of IL-2 and rapamycin has the potential to inhibit human islet allograft rejection by expanding CD4+FOXP3+ Tregs in vivo and suppressing effector cell function and could be the basis of effective tolerance-based regimens.

P2X7 receptor antagonism increases regulatory T cells and reduces clinical and histological graft-versus-host disease in a humanised mouse model

“…It is hypothesised that in this model, P2X7 activation results in the loss of hTregs as a result of cell death. P2X7 activation can mediate the death of Tregs (34) , while the presence of hTregs decreases over time in this model (23) , most likely due to the absence of factors that support hTreg survival in mice (38) .…”

“…IFNγ has known roles in GVHD progression, with IFNγ-producing CD4 + and CD8 + T cells present early in GVHD development (37) and IFNγ promoting the trafficking of T cells to GVHD tissues (39) . Notably, transplantation or expansion of Tregs reduces serum IFNγ in allogeneic and humanised mouse models of GVHD (23,40) . Therefore, the observed reduction in serum hIFNγ may be due to the increase in hTregs.…”

“…Samples were examined for signs of GVHD as indicated. Histological GVHD in the liver, flank and ear skin, and duodenum was assessed, in a blinded fashion, using a standardised grading system (using grades from 0 to 4) as described (23) (Table S2). Lung GVHD was determined by blinded area measurements of clear alveoli space using Fiji (24) and quantified as a percentage of the total lung area measured.…”

Tregs and Mixed Chimerism as Approaches for Tolerance Induction in Islet Transplantation

“…This may be because many studies do not use lymphodepletion, which may help with T reg engraftment ( 71 , 72 ). Furthermore, the persistence of T regs may be affected by the concomitant use of immunosuppressive drugs ( 73 ), with some evidence pointing to low dose IL-2 and rapamycin as a more effective strategy than other immunosuppressive regimins ( 74 ). Likewise, the use of low dose IL-2 and protein engineered IL-2 derivatives is being explored ( 75 ).…”

Regulatory T cells and transplantation tolerance: Emerging from the darkness?

“…At a much earlier stage are the studies based on using a monoclonal antibody that selectively targets effector T cells and spares Tregs [121], or the use of low‐dose IL‐2 to override the inhibitory effect of calcineurin inhibitors on lL‐2 secretion [122].…”