Serum and bronchoalveolar lavage fluid levels of soluble B7H3 in patients with interstitial lung diseases

The B7 family member B7H3/CD276 was recently reported to be involved in the pathophysiology of idiopathic pulmonary fibrosis (IPF). However, the association of B7H3 with prognosis in patients with fibrosing interstitial lung diseases (ILDs), including IPF, remains unclear. This study was investigated to determine the potential of soluble B7H3 (sB7H3) as a biomarker to predict prognosis in patients with fibrosing ILDs.Patients with ILDs from various categories who underwent bronchoalveolar lavage (BAL) were included in the study. The relationship between sB7H3 levels in serum or BAL fluid (BALF) and clinical variables at the time of ILD diagnosis was studied retrospectively. All patients who met the fibrosing ILD criteria were followed for 5 years.We found that coexisting malignancy affected the serum, but not the BALF, sB7H3 levels. There was no significant correlation between serum and BALF levels of sB7H3 in 49 ILD patients without malignancy (11 with sarcoidosis, 5 with drug-induced ILD, 22 with IPF, and 11 with ILD associated with systemic sclerosis). We also found that the BALF levels, but not serum levels, of sB7H3 at the time of ILD diagnosis had independent prognostic potential on 5-year survival in patients with fibrosing ILDs. Of note, patients with a higher level of BALF sB7H3 at diagnosis (≥0.100 ng/mL) showed significantly shorter survival than those with lower levels.This study suggests that BALF sB7H3 could be a novel prognostic biomarker in a broad range of fibrosing ILD patients.