CD4 and silicosis: Additionally, a reduced number or function of Tregs has been described in a study with silicosis patients [40], but this discrepancy could be due to an age-corrected Treg percentage applied to the silicosis group in that study and to the imprecision of including as Treg cells a fraction with only two cell surface markers (CD4+CD25+) and at least a FoxP3+ or a CD127− marker could be additionally used [20].