There are controversial results concerning alterations in the percentage of Treg cells, with some studies describing an increased percentage of CD4+ Treg in SSc patients [64,78,79,80], for which there is a positive correlation with disease severity [79] and interstitial lung disease [64], and others showing decreased or unchanged Treg levels [23,59,60,66,67]. The gene discussed is CD4; the disease is systemic sclerosis.