Several studies have used mice in addressing questions of liver structure and function in general, and of Kupffer cells in particular [[12–21]]. Although several studies have examined varied aspects of Kupffer cell function in mice, there has not been, to our knowledge, a study Pictilisib ic50 of the basic characteristics and the postnatal development of Kupffer cells in mice. Because of the important

role that will be played by mice in future studies of liver function, it is imperative to establish the baseline of normal Kupffer cell composition to serve as a reference for these future studies. The purpose of this study was to identify and characterize Kupffer cells in the livers of postnatal mice, and to determine the age in mice at which Kupffer cells are phagocytically active. Results Immunocytochemical identification of Kupffer cells The photomicrographs presented in Figure 1 are taken from mice euthanized at 28 days of age. These images demonstrate that at this relatively young age the F4/80 antibody labels a population of cells with widely branching and broad dendritic processes and apparently small oblong nuclei, quite similar to those reported for Kupffer cells in adults [12, 21]. The F4/80 labelled cells are distributed rather homogeneously throughout the liver tissue, with the exception that these cells typically are not seen

close to (within 50 μm of) the central venules. Figure 1 Fluorescence photomicrographs showing Kupffer cells from sections of P28 AZD0530 clinical trial mouse liver. A: Alexa 488 (green) labelled F4/80 positive cells. Note branching of cells, and relative absence of positive cells close to the central venule (cv). Calibration bar = 100 μm. B: Merged image showing Alexa 488 (green) labelled F4/80 positive cells along with 0.2 μm red fluorescent microsphere positive cells. Arrows indicate examples of double labelled

cells. Calibration bar = 50 μm. Further, Figure 1B demonstrates that these F4/80 positive cells second can be labelled by intravascularly administered fluorescent microspheres (in this case, 0.2 μm microspheres with a post-injection survival period of 1 hour), indicating their phagocytic ability. Although not all F4/80 positive cells can be seen to contain microspheres, and not all (red) microspheres can be seen to be contained within F4/80 positive cells, the correspondence of the two labels is remarkable. Greater than 90% of F4/80 positive cells contained microspheres. Size of microspheres The pattern of labelling within the liver was influenced by the size of microspheres. For example, when mice were injected intravascularly with the relatively large 0.2 μm microspheres, these microspheres were found co-localized primarily with F4/80 positive cells. The regional distribution of these co-labelled cells from a P30 mouse is illustrated in Figure 2A,B,C. Images taken at higher magnification, and from younger P15 mice, in Figure 2D,E,F demonstrate morphological features of these cells.