Methods and compositions for preventing type 1 diabetes

A method of delaying the onset of clinical type 1 diabetes (T1D), comprising:

• administering a prophylactically effective amount of teplizumab to a non-diabetic subject at risk for T1D, wherein the prophylactically effective amount comprises a 10 to 14 day course of teplizumab;
• and
• measuring a frequency of TIGIT+KLRG1+CD8+ T-cells in all CD3+ T-cells in the non-diabetic subject at three months or more after the administration of the 10 to 14 day course of teplizumab,
• wherein a measured frequency of about 5% to about 50% TIGIT+KLRG1+CD8+ T-cells in all CD3+ T-cells in the non-diabetic subject at three months or more after the administering of the 10 to 14 day course of teplizumab is indicative of successful delay of the onset of clinical T1D.