CD4 and idiopathic pulmonary fibrosis: IL-17 was mainly secreted by T cells in BLM/NT127-instilled mice, and the percentages and numbers of IL-17+γδ T cells were markedly higher than those of IL-17+CD4+ T cells, suggesting that γδ T cells were the predominant source of IL-17 in AE-IPF (Figure 3A).