CD4 and idiopathic pulmonary fibrosis: The two diseases share similar common features, such as T cell profiles (Th2, Th17, increased ratio of CD4 to CD8 T cells), T cell cytokine profiles (IL-4, IL-5, IL-10, and IL-17 of IPF, and IL-4, IL-5, IL-6, IL-10, IL-13, and IL-22 in SSc-ILD (Bagnato and Harari, 2015).