CCR4 deficiency can protect mice from fibrotic responses [73], but a skewed CCR4 to CCR6 CD4+ T-cell ratio in the lung tissue of IPF patients is associated with better lung function [76], suggesting a controversial role for the immune system, potentially distinct fibrotic responses between mice and humans and protective features of specialized T subsets. Here, CCR6 is linked to idiopathic pulmonary fibrosis.