We measured the proportions of three effector (Th1, Th2 and Th17), and three regulatory (Treg, IL-10+ and transforming growth factor (TGF)-β+) CD4+ subsets in the peripheral blood of people with CF, compared them with those in age-matched controls, and analyzed the CF group for associations of each subset with demographic and clinical variables. Here, CD4 is linked to cystic fibrosis.