In IPF patients, there was a trend toward a correlation between the percentage of S100A9+CD163− monocytes and the surfactant protein-D (SP-D) serum levels (r = 0.4158, [95% confidence interval (CI) − 0.02042–0.7191], p = 0.051). Here, S100A9 is linked to idiopathic pulmonary fibrosis.