Lung sections from mice expressing raTA and Cre transgenes and the floxed
IKK-2 gene that did not receive (a and c) or that received (b and d) doxycycline
in utero were probed by in situ hybridisation for IKK-2 mRNA. Sections were
counterstained with haematoxylin and eosin. Images of ×20 (a and b) and ×40
(c and d) magnification are shown.