Association between nonspecific interstitial pneumonia and presence of CD20+ B lymphocytes within pulmonary lymphoid follicles

Nonspecific interstitial pneumonia (NSIP) is characterised by interstitial infiltration of lymphocytes and varying amounts of interstitial fibrosis. B cells have been suggested to contribute to the pathogenesis of NSIP. However, the relationship between B-lymphocyte and the clinical outcomes of NSIP was unclear. In this study, 50 patients with histopathologically confirmed NSIP from Peking Union Medical College Hospital between April 2003 to December 2012 were retrospectively analyzed. Using immunohistochemical analyses, CD20+ B cells were counted in the lymphoid follicles, perivascular, interstitial, and peribronchiolar regions of lung tissure. The CD20+ lymphocytes were mainly present in the lymphoid follicles. The number of follicular CD20+ lymphocytes was higher in the fibrosing than cellular NSIP pattern [255.08 (132.92-449.71) vs. 121.33 (63.54-282.88)/0.1 mm², p = 0.017]. After 1 year of therapy, the follicular CD20+ lymphocytes were significantly higher in patients whose forced vital capacity (FVC) worsened as compared to those who improved (p = 0.014). Additionally, follicular CD20+ lymphocytes were negatively correlated with the post-treatment percentage change in FVC (rho = -0.397, p = 0.004). However, follicular CD20+ lymphocytes were not correlated with survival. These results suggested that pulmonary follicular CD20+ lymphocytes were correlated with the fibrosing pattern of NSIP and predicted less clinical improvement after treatment.