The loss of Rac1 activity reduces emphysema development. Mice reconstituted with WT or Rac1^−/− hematopoietic cells were exposed to fMLP (20 μg per mouse) into the lung. WT non-exposed mice were used as control. Five weeks after exposure, lung histology was performed. Sections were stained with hematoxylin and eosin, ×200 (n = 16 from 2 independent experiments).