Transient Depletion of Foxp3+ Regulatory T Cells Selectively Promotes Aggressive β Cell Autoimmunity in Genetically Susceptible DEREG Mice

Abstract

Type 1 diabetes (T1D) represents a hallmark of the fatal multiorgan autoimmune syndrome affecting humans with abrogated Foxp3+ regulatory T (Treg) cell function due to Foxp3 gene mutations, but whether the loss of Foxp3+ Treg cell activity is indeed sufficient to promote β cell autoimmunity requires further scrutiny. As opposed to human Treg cell deficiency, β cell autoimmunity has not been observed in non-autoimmune-prone mice with constitutive Foxp3 deficiency or after diphtheria toxin receptor (DTR)-mediated ablation of Foxp3+ Treg cells. In the spontaneous nonobese diabetic (NOD) mouse model of T1D, constitutive Foxp3 deficiency did not result in invasive insulitis and hyperglycemia, and previous studies on Foxp3+ Treg cell ablation focused on Foxp3DTR NOD mice, in which expression of a transgenic BDC2.5 T cell receptor (TCR) restricted the CD4+ TCR repertoire to a single diabetogenic specificity. Here we revisited the effect of acute Foxp3+ Treg cell ablation on β cell autoimmunity in NOD mice in the context of a polyclonal TCR repertoire. For this, we took advantage of the well-established DTR/GFP transgene of DEREG mice, which allows for specific ablation of Foxp3+ Treg cells without promoting catastrophic autoimmune diseases. We show that the transient loss of Foxp3+ Treg cells in prediabetic NOD.DEREG mice is sufficient to precipitate severe insulitis and persistent hyperglycemia within 5 days after DT administration. Importantly, DT-treated NOD.DEREG mice preserved many clinical features of spontaneous diabetes progression in the NOD model, including a prominent role of diabetogenic CD8+ T cells in terminal β cell destruction. Despite the severity of destructive β cell autoimmunity, anti-CD3 mAb therapy of DT-treated mice interfered with the progression to overt diabetes, indicating that the novel NOD.DEREG model can be exploited for preclinical studies on T1D under experimental conditions of synchronized, advanced β cell autoimmunity. Overall, our studies highlight the continuous requirement of Foxp3+ Treg cell activity for the control of genetically pre-installed autoimmune diabetes.

Selective ablation of thymic and peripheral Foxp3+ regulatory T cell development

“…Consistently, mild immune infiltrations were limited to the salivary gland (mouse #1), and the lung (mouse #1) of individual ΔtTreg mice, but could not be observed in other organs, such as the liver or thyroid gland ( Figure 4A ). Interestingly, although B6.ΔtTreg mice maintained normoglycemia, histological analyses consistently revealed pronounced immune infiltrates in the pancreas ( Figure 4A , bottom panels), which is in contrast to previous studies in other settings of tTreg cell deficiency, including Foxp3-deficient mice ( 33 ) and acute Treg cell ablation in the ‘Depletion of Regulatory T cells’ (DEREG) mouse model on the B6 and NOD genetic background ( 13 ).…”

“…We therefore tracked blood glucose levels in cohorts of 3-week-old, initially normoglycemic F2 NOD.ΔtTreg mice that showed no signs of WD, PN, or other scurfy -like symptoms ( Figure 8A ). In our colony of conventional NOD mice, the first diabetes cases become apparent at approximately 12 weeks of age and continuously increase to an incidence of 70-90% in females and 0-20% in males within 30 weeks of age ( 13 , 57 ). Whereas in (B6>NOD)F2 ΔtTreg mice, selective tTreg cell paucity unleashed a particularly severe form of T1D: > 50% of males rapidly progressed to overt diabetes within < 8 weeks after birth ( Figure 8A ), despite the usually observed female sex bias and kinetics difference in the NOD model ( 58 ).…”

Exenatide regulates Th17/Treg balance via PI3K/Akt/FoxO1 pathway in db/db mice

“…Deficiency of Tregs may result in the progress of inflammation and diabetes. A previous study from Watts et al reported that depletion of Foxp3 + Tregs precipitates destructive β-cell autoimmunity in NOD.DEREG (‘depletion of regulatory T cell’) mouse model (Watts et al 2021 ). Conversely, transfer of Tregs could largely prevent Teffs-induced diabetes development in NOD mice (Sprouse et al 2018 ).…”

Exenatide regulates Th17/Treg balance via PI3K/Akt/FoxO1 pathway in db/db mice

“…De ciency of Tregs may result in the progress of in ammation and diabetes. A previous study from Watts et al reported that depletion of Foxp3 + Tregs precipitates destructive β-cell autoimmunity in NOD.DEREG ('depletion of regulatory T cell') mouse model (Watts et al 2021). Conversely, transfer of Tregs could largely prevent Teffs-induced diabetes development in NOD mice (Sprouse et al 2018).…”