Efficacy of Extracorporeal Photopheresis (ECP) in the Treatment of Type 1 Diabetes Mellitus

* Inclusion Criteria * Confirmed and documented diagnosis of T1DM. Patients must have: * A documented history of T1DM within the first 3 years of onset. * Should be on a multiple dose injection (MDI) therapy. * C-Peptide levels of ˂ 0.7 ng/mL. * HbA1C ≥ 6.5% to ≤ 10%. * Evidence of pancreatic autoimmunity, if available (positive anti-glutamic acid decarboxylase \[GAD\]; Islet antigen 2 \[anti-IA2\]; and/or zinc transporter 8 \[ZnT8\] antibodies). * Male or female aged ≥ 18 to ≤ 50 years. * Weight \> 40 kg. * Hematocrit ≥ 32%. * Platelet count ≥ 100 x10\^9/L (with or without transfusion support). * Willingness to participate in all OPERA Study tests, visits, and ECP procedures, as outlined in the informed consent. * Willingness to use at least one reliable method of birth control (e.g. abstinence, oral contraceptives, intrauterine devices, barrier method with spermicide, or surgical sterilization) throughout the study for all men and women of childbearing potential. * The patient agrees to participate in the trial, and signs the OPERA Study informed consent form. * Exclusion Criteria * Pediatric aged \< 18 or ˃ 50 years. * Clinical diagnosis of type 2 diabetes mellitus (T2DM). * Inability to tolerate fluid changes associated with ECP (e.g. inadequate renal, hepatic, pulmonary and cardiac function leading to enable patient to tolerate extracorporeal volume shifts associated with ECP). * Hypersensitivity or allergy to citrate products. * Hypersensitivity or allergy to psoralen compounds such as Methoxsalen (8-Methoxypsoralen, 8-MOP). * Aphakia (8-MOP is contraindicated because of the significantly increased risk of retinal damage due to the absence of lenses). * Presence of comorbidities that may result in photosensitivity (systemic lupus erythematosus, porphyries, albinism, etc.). * Suspected or diagnosed Diabetic Ketoacidosis (DKA) at the moment of the screening visit. * Uncontrolled infection requiring treatment at study entry. * Laboratory evidence of any of the following: * White Blood Cell (WBC) count \< 3.00 x10\^9/L. * Serum transaminase levels \> x2 upper normal limit (UNL). * Hematocrit \< 32%. * Platelet count \< 100 x10\^9/L (with or without transfusion support). * Diagnostic of Hepatitis B Virus (HBV) infection. * Diagnostic of Human Immunodeficiency Virus (HIV) infection or Acquired Immunodeficiency Syndrome (AIDS). * Pregnant or lactating women. * Have participated in other clinical trial in the past 3 months. * Organ transplants in the past 3 months. * Current diagnosis of cancer. * Inability to comply with all OPERA Study tests, visits, and procedures (including ECP). * Inability to provide informed consent.