Damaged RBCs are sequestered in the hepatic sinusoid in a PS-dependent manner regardless of the presence of Kupffer cells. (A) Clodronate liposome-treated or control (PBS-treated) mice were injected with FITC-labeled normal or damaged RBCs (green), after which the livers were harvested 15 minutes later. Frozen sections were stained with Abs directed against CD31 (red; a marker for endothelial cells) and F4/80 (yellow; a marker for Kupffer cells) and analyzed by confocal microscopy. Scale bars, 10 μm. (B) Microscopic quantitation of sequestration of normal or damaged RBCs in liver section. Each experiment was independently performed 3 times. Results represent mean ± SD for 6 mice per group; t test: *P < .01 versus NR. NR indicates normal RBCs; and DR, damaged RBCs. (C) Clodronate liposome-treated or control (PBS-treated) mice were injected with NBD-PC–labeled PS or PC beads (green), after which the livers were harvested 15 minutes later. Frozen sections were stained with Abs directed against CD31 (red) and F4/80 (yellow). PC or PS beads, CD31⁺ cells, and F4/80⁺ cells were visualized by confocal microscopy. Liver from control mice effectively sequestered PS-coated beads, which were colocalized with Kupffer cells. Even in clodronate-treated mice PS-coated beads were found in the sinusoid to the same degree as in control mice. Scale bar, 10 μm. (D) Clodronate liposome-treated or control (PBS-treated) mice were injected with NBD-PC–labeled PC-coated or PS-coated beads, and their sequestration in liver section was quantified by confocal microscopy. Each experiment was independently performed 3 times. Results represent mean ± SD for 6 mice per group; t test: *P < .01 versus PC. PC indicates PC-coated beads; and PS, PS-coated beads.