Fig. 3.  Fluorescence-mediated tomography detects endogenous leukocyte extravasation defects. (A ) Three days after thioglycollate injection, peritoneal macrophage counts from urokinase-type plasminogen activator receptor-deficient (u-PAR−/−) mice are significantly lower compared with controls (P < 0.05, n = 8/9). (B ) Fluorescence-mediated tomography unmasked this difference in macrophage recruitment noninvasively in live animals. Enhancement of the mean fluorescence intensity (MFI) was more pronounced in wild-type (wt) than in u-PAR−/− mice. It is noteworthy that the contribution of leukocytic u-PAR is more significant than u-PAR expressed on other cells, as evidenced by the observation that the reduction of recruitment is stronger if u-PAR−/− macrophages are adoptively transferred into wt mice than vice versa . (n = 6, P < 0.05). (C ) Twenty-four hours after lipopolysaccharide injection, fluorescence-mediated tomography quantification revealed diminished recruitment of DiR-labeled neutrophils into the lungs of u-PAR−/− mice compared with wt mice (n = 6, P < 0.05).