Anti-CD3 mAb is genetically engineered and directed against the CD3 antigen on T cells; this antibody selectively attacks the immune cells responsible for beta cell destruction. In a small exploratory clinical trial, patients with newly diagnosed type 1 diabetes who received a single, 2-week treatment with anti-CD3 mAb had preserved beta cell function and significantly lower insulin requirements than untreated patients for up to two years after therapy. This study will investigate whether a second course of anti-CD3 mAb administered one year after the first administration is able to prolong or improve the effects of the biologic in people who have recently diagnosed type 1 diabetes mellitus.