SELL and diabetes mellitus: Both CD62L+ and CD62L- Tregs have shown a similar suppressive capacity for T-cell activation in vitro (83, 84), but the CD62L+ Tregs – not the CD62L- counterparts – are likely the major population that provides long-lasting immune tolerance, protecting against lethal acute graft-versus-host disease (85, 86) and delaying diabetes in prediabetic nonobese diabetic mice (84).