The proportion of CCR6+ CD4+ T cells within the blood of our IPF cohort (mean, 1.00 ± 0.42%) was significantly decreased when compared to the proportion of lung and LLN CCR6+ CD4+ T cells (mean, 6.83 ± 2.78%; and mean, 8.31 ± 1.84%; p = 0.0009, respectively) (Figures 2B,E). Here, CD4 is linked to idiopathic pulmonary fibrosis.