Response to: 'Circulating regulatory T cells were absolutelydecreased in dermatomyositis/polymyositispatients and restored by low-dose IL-2 by Zhang et al

In this issue, Zhang et al report that a short course of low-dose IL-2 improved patients with polymyositis or dermatomyositis. This adds to the list of diseases for which efficacy of low-dose IL-2 has been reported.1 This is in line with the main activity of low-dose IL-2, the stimulation and expansion of regulatory T cells (Tregs).1 Tregs are key to maintaining immune homeostasis. They control inflammation and the activation of effector T cells with autoimmune potential.2 Their depletion immediately unleashes major activation of effector T cells leading to fatal inflammation and the attack of otherwise healthy tissues, leading to multiorgan autoimmunity.3 This observation indicates that, at homeostasis, there is a balance between Tregs and effector T cells that prevents severe inflammation and autoimmunity. This, in turn, teaches us that any chronic breach of this homeostasis, that is, an autoimmune condition, inherently...