The purpose of this study is to assess the safety of Tregs + IL-2 and survival of Tregs in patients with recent onset T1DM who receive infusions of autologous Tregs + IL-2.

The investigators hypothesize that ex vivo expanded human autologous CD4+CD127lo/-CD25+ polyclonal regulatory T cells (Polyclonal Tregs) plus Interleukin-2 (IL-2) administered to patients with Type 1 Diabetes Mellitus (T1DM) will be safe and biologically active. A Phase I trial with this cellular therapy plus IL-2 will lead the way for Phase II trials that test for efficacy based on preservation of C-peptide, reduced exogenous insulin requirements and improved glycemic control.

This is a Phase I safety/dosing study of Polyclonal Tregs + IL-2 in patients with T1DM.

The Tregs will be expanded using an established protocol utilizing anti-CD3/anti-CD28 beads plus IL-2. The study will involve 2 dosing cohorts of 6-8 T1DM patients each. The primary objective of this study is to assess the safety of Tregs + IL-2 and survival of Tregs in patients with recent onset T1DM who receive infusions of autologous Tregs + IL-2. The study will also assess potential effects of Tregs on beta cell function and the autoimmune response.

Subjects will receive Polyclonal Tregs at doses of 3 or 20x10^6 cells/kg. The dose of Tregs is selected based on a combination of considerations of manufacturing capacity, a predicted efficacious dose, and the available safety data of the Treg product currently in clinical trials. The IL-2 dose will be 1 x10^6 IU subcutaneously, given daily for 5 consecutive days at the completion of the cell infusion and again after 1 month. This dose is based on recent studies from Klatzmann et al. in T1DM, where the dose was found to be effective in a selective Treg expansion, well tolerated, and without an acute decline in beta cell function (Rosenzwajg et al., 2015).

Inclusion Criteria:

1. Diagnosis of T1DM within >3 and <24 months of day 0 according to the American Diabetes Association standard criteria.
2. 18 to 45 years of age on day of screening visit.
3. Positive for at least one islet cell autoantibody (glutamate decarboxylase; insulin, if obtained within 10 days of the onset of insulin therapy; ICA 512-antibody; and/or ZnT8).
4. Peak stimulated C-peptide level >0.2 pmol/mL (0.6 ng/ml) following an MMTT.
5. Weight of >= 40 kg and <=90.7kg
6. Adequate venous access to support a blood draw of 5 mls/kg up to maximum of 400 ml whole blood and later infusion of investigational therapy

Exclusion Criteria:

1. Hemoglobin <10.0 g/dL; leukocytes <3,000/μL; neutrophils <1,500/μL; lymphocytes <800μL; platelets <100,000/μL
2. Any sign of significant chronic active infection (e.g., hepatitis, tuberculosis, EBV, or CMV), or screening laboratory evidence consistent with a significant chronic active infection (such as positive for HIV, PPD, or HBsAg).
3. Anticipated ongoing use of diabetes medications other than insulin that affect glucose homeostasis, such as metformin, sulfonylureas, thiazolidinediones, glucagon-like peptide 1 (GLP-1) mimetics, dipeptidyl peptidase IV (DPP-IV) inhibitors, SGLT2 inhibitors, or amylin.
4. Chronic use of systemic glucocorticoids or other immunosuppressive agents, or biologic immunomodulators within 6 months prior to study entry. Specifically, subjects who have received over 7 days of treatment with 7.5 mg of prednisone (or the equivalent) within 6 months prior to study entry will be excluded.
5. History of malignancy (including squamous cell carcinoma of the skin or cervix) except adequately treated basal cell carcinoma
6. Pregnant or breastfeeding women, or any female who is unwilling to use a reliable and effective form of contraception for 1 year after Treg +/- IL-2 dosing, and any male who is unwilling to use a reliable and effective form of contraception for 3 months after Treg +/- IL-2 dosing
7. Any condition that, in the investigator's opinion, may compromise study participation or may confound the interpretation of the study results.
8. Patients who are unwilling to agree to not participate in another clinical trial, which in the opinion of the investigator may confound the results of this study, for at least 1 year following Treg infusion.