CD4 and idiopathic interstitial pneumonia: The median proportion of Tfh cells (CD3+CD4+CXCR5+) to total T cells (CD3+CD4+) was 20.4% (IQR, 13.4–27.2%) in the IPF patients and 15.4% (IQR, 14.2–19.7%) in the healthy controls and significantly higher in the IPF patients (p = 0.042; Fig. 1).