However, activated CD4+ T cells (CD69+CD25+HLA-DR-/+) were significantly increased in IPF compared to COPD and donor lungs (p = 0.0006; 11.8% [9.2–20.4] vs. 7.6% [2.8–10.1] and 2.7% [0.6–10.5], respectively; Table 2). Here, CD4 is linked to idiopathic pulmonary fibrosis.