CD4 and type 1 diabetes mellitus: In settings of therapeutic trials to impact T1D, ATG (Thymoglobulin, Sanofi Genzyme) was first used at a “high” dose of 6.5 mg/kg (START trial) but failed to demonstrate clinical efficacy in the primary endpoint, potentially due to the dose-associated depletion of both CD4+ T effector (Teff) and T regulatory (Treg) cell populations (6–8).