We found that plasma levels of NETs markers including dsDNA, NE, and MPO were significantly higher in the BO group than in the control group (p < 0.001, p = 0.001, and p = 0.003, respectively; Figure 1c–e), demonstrating that ANCA, as well as NETs, are highly expressed in the circulation during the process of BO. Here, MPO is linked to bronchiolitis obliterans syndrome.