The purpose of this study is to investigate the safety and therapeutic effect of ex-vivo expanded umbilical cord blood regulatory T cells on autoimmune diabetes.

The regulatory T cells (Treg) used in this study will be produced from human umbilical cord blood. The umbilical cord blood will be freshly collected and immediately separated to buffy coat in a GMP laboratory, thus to be further sorted into Treg and other subsets. Then the Treg will be expanded ex-vivo for approximately 14 days until tested for its surface markers and suppressive ability. During the time of ex-vivo expansion, eligible autoimmune diabetes patients will be recruited and admitted to our hospital in order to go through required examinations. Once the Treg product has reached the safety and efficacy standards, the patient will receive the Treg product infusion under close surveillance of doctors and then go through regular follow-ups to investigate the safety and therapeutic effect of the Treg product on autoimmune diabetes patients.

Inclusion Criteria:

1. Autoimmune diabetes patients are screened for enrollment in the study if both clinical signs and laboratory tests meet the diagnosis standards of American Diabetes Association
2. Diagnosis of Autoimmune Diabetes within 3 years of screening
3. Between 6 to 60 years of age
4. Positive for at least one of the anti-islet autoantibodies: GADA, IA2A, ZnT8A
5. Fasting or postprandial plasma C-peptide more than 200 pmol/L
6. Written informed consent from the patient or the patient's parents for patients under the age of 18 years

Exclusion Criteria:

1. Any clinically significant diseases in liver (ALT and AST over 2 times upper normal limit), kidney (Scr over 133umol/L), and heart
2. Presence of anemia (Hb ≤100g/L), leukopenia (<3.5×10^9/L)
3. Presence of disorder in coagulation or anticoagulation, or thrombocytopenia (platelets <100×10^9/L)
4. Presence of acute metabolic disorders; In the case of acute ketone acidosis, with blood ketone over 0.3mmol/L and pH lower than 7.30
5. Presence of any kind of chronic infection or immune deficiency, including hepatitis B, hepatitis C, HIV, syphilis or tuberculosis
6. Chronic use of systemic glucocorticoids or other immunosuppressive agents for over 3 months
7. Any history of malignancy
8. Female patients who are pregnant or breastfeeding; any female who is unwilling to use a reliable and effective form of contraception for 2 years afer recruitment
9. Presence of any infectious diseases, including active skin infections, flu, fever, upper or lower respiratory track infections; those who wish to participate in the study should keep the infection under control for at least 1 week before receiving Treg product infusion
10. Presence of diabetic microvascular or macrovascular diseases
11. Presence of hypertension
12. Any medical condition that, in the opinion of the investigator, will interfere with safe participation in the trial