The simplest and most uniform immunological outcome in all trials is an increase in the frequency and/or absolute number of Tregs in peripheral blood which was observed in almost all studies of low-dose subcutaneous IL-2 therapy, with the unique exception of a study in alopecia areata patients [84] where Tregs were recruited to and significantly increased within scalp skin lesions but not in the blood. Here, IL2 is linked to alopecia areata.