Participants will be randomly assigned to one of two groups. The Experimental Group will receive anti-CD3 mAb treatment plus Diabetes Standard of Care Treatment; the Active Comparator Group will receive Diabetes Standard of Care Treatment. The Experimental Group will be treated with the antibody for the first 14 days of the study and again one year later. These participants will be admitted to the hospital for the first 5 days of a treatment cycle. Participants who live within 1 hour of the hospital may receive the remainder of a treatment cycle as an outpatient, but those who live farther away will be hospitalized for 14 days. For the first treatment cycle, there will be study visits on the 3 consecutive days after the treatment cycle and at Months 1, 2, 3, 6, 9, and 12. For the second treatment cycle, there will be study visits on the 3 consecutive days after the treatment cycle and at Months 13, 16, 19, 21, and 24.The Active Comparator Group will have 12 study visits over two years.