CD4 and idiopathic pulmonary fibrosis: Notably, Morse et al. [46] also observed significant alterations in the CD4 + Treg subset (FOXP3+) in IPF lung tissues compared to controls, suggesting a potential role for regulatory T cells in disease pathogenesis.In addition to its immunomodulatory functions, CXCL13 can activate lung fibroblasts via the CXCR5 receptor, leading to upregulation of α-SMA and type I collagen expression and thereby promoting extracellular matrix accumulation.