Fig. 4

S. pneumoniae-induced empyema is characterized by persistent pleural fibrosis, rind formation and lung restriction at 7 days. Antibiotic treatment was begun 18 h after S. pneumoniae was intrapleurally administered. a Peripheral lung sections from saline and S. pneumoniae infected mice were picrosirius stained to detect collagen deposition (red–orange birefringence). S. pneumoniae infected mice demonstrated increased collagen deposition at the pleural surface and in the subpleural region compared to saline-treated mice. Solid arrows indicate the basement membrane and the visceral pleural surface. Areas of collagen deposition were detected at the basement membrane and within the thickened pleural mesothelium. b Tissue sections from 7 days saline and S. pneumoniae infected mice were stained for fibrin (ogen) by immunohistochemical analysis (red stain). Extravascular fibrin (ogen) deposition is readily apparent after S. pneumoniae infection. Solid arrows indicate the pleural surface and the basement membrane of the thickened pleura of S. pneumoniae infected mice. Fibrin(ogen) deposition was prominent at the pleural surface of S. pneumoniae infected mice. c Lung volumes and function (compliance) were significantly decreased by S. pneumoniae infection by 14 days (p < 0.01)