CD8+ tissue-resident memory T cells are essential in bleomycin-induced pulmonary fibrosis

Human tissue-resident memory T (T RM ) cells play a crucial role in protecting the body from infections and cancers. Recent research observed increased numbers of T RM cells in the lung tissues of idiopathic pulmonary fibrosis patient. However, the functional consequences of T RM cells in pulmonary fibrosis remain unclear. Here, we found that the numbers of T RM cells, especially the CD8 + subset, were increased in the mouse lung with bleomycin-induced pulmonary fibrosis. Increasing or decreasing CD8 + T RM cells in mouse lungs accordingly altered the severity of fibrosis. In addition, adoptive transfer of CD8 + T cells containing a large number of CD8 + T RM cells from fibrotic lungs was sufficient to induce pulmonary fibrosis in control mice. Treatment with CCL18 to induced CD8 + T RM cell expansion and exacerbated fibrosis, while blocking CCR8 prevented CD8 + T RM recruitment and inhibited pulmonary fibrosis. In conclusion, CD8 + T RM cells are essential for bleomycin-induced pulmonary fibrosis, and targeting CCL18/CCR8/CD8 + T RM cells may be a potential therapeutic approach.