Idiopathic pulmonary fibrosis (IPF) is a disease that is insensitive to both hormonal and other therapies. Xue J et al. from the University of Pittsburgh, USA, suggested that the development of IPF may be related to B cells. It was found that the proportion of circulating plasma cells to B cells was higher in patients with IPF (3.1 ± 0.8%) than in normal subjects (1.3 ± 0.3%) (p < 0.03) and that this difference was associated with lung volume in patients with IPF ( R = 0.44, p < 0.03). diffuse aggregation of CD20(+) B cells distributing lung parenchyma, perivascular immune complexes, complement deposition, all in IPF prevalent in the lungs, but less prominent or absent in normal subjects. Plasma B lymphocyte-stimulating factor (BlyS) concentrations in plasma were significantly higher in 110 patients with IPF (2.05 ± 0.05 ng/ml) than in 53 normal subjects (1.40 ± 0.04 ng/ml) and 90 patients with obstructive lung disease (1.59 ± 0.05 ng/ml) (p < 0.0001). levels of BlyS and pulmonary artery pressure were correlated in patients with IPF (r = 0.58, p < 0.0001). Patients with the highest BlyS (25% fraction) had a lower 1-year survival rate (46 ± 11%) than patients with lower BLyS concentrations (81 ± 5%) (hazard ratio = 4.0, 95% confidence interval 1.8 -8.7, p = 0.0002).