Tissue responses. Lung tissues from mice treated with intratracheal LPS in the presence or absence of oral doxycycline. The lungs of mice studied 24 h after the administration of intratracheal LPS showed intra-alveolar inflammatory infiltrates (arrows), which were absent in mice that received oral doxycycline starting 72 h prior to the administration of LPS. However, there were abundant neutrophils in the alveolar walls of the mice treated ith LPS and doxy (arrowheads). Note that in either case the alveolar walls remained thin.