CD4 and idiopathic interstitial pneumonia: By identifying specific lymphocyte profiles, including BAL eosinophil and ILC3 frequencies in CEP, BAL CD4/CD8 ratios in SAR, and distinct peripheral blood Th1, Th17, and Treg cell patterns in IIP, CHP, and CTD, we found that these markers could aid in the accurate classification and differential diagnosis of ILDs.