Using quantitative flow cytometry analysis (Fig 1), overall circulating fibrocyte counts, defined as CD45and collagen-1expressing (CD45+Col-1+) cells in the peripheral blood was up to 5-fold higher in patients with BPD compared with in patients with ARDS (p < 0.01) and normal subjects (p < 0.01) (Fig 2A). Here, PTPRC is linked to bronchopulmonary dysplasia.