HA is expressed in the sinusoids, but not in the postsinusoidal venules, of the liver. The location of HA expression within the liver microvasculature was determined via fluorescence intravital microscopy of the liver using a spinning disk confocal microscope. Mice were left untreated or treated for 4 h with i.v. LPS. (A and B) The liver architecture shown by autofluorescence before the addition of any fluorophores. HA localization was observed by administration of Alexa Fluor 488–labeled HABP in untreated (C) or LPS-treated (D) mice. PE- labeled anti–Gr-1 antibody was also used to examine neutrophil presence in the liver (E and F). Squares represent areas enlarged in inlay (C–F). Arrows and arrowheads denote the location of the sinusoids and postsinusoidal venules, respectively. Bars, 100 μm. Images are representative of at least three experiments.