Based on recent data on the functional consequences of the differential expression of the distinct FoxP3 isoforms, and thanks to the availability of isoform-specific antibodies, we have investigated FoxP3 expression by Treg cells in patients with multiple sclerosis (MS) and in healthy donors (HD), focusing on the Treg subtypes identified by differential expression of surface markers. Here, FOXP3 is linked to multiple sclerosis.