Liposomal-clodronate blocking of phagocytosis of antibody-opsonized RBCs by splenic macrophages.

Mice were injected with PKH-labeled liposomes (containing either clodronate or PBS), and 2 hours later, DiD-labeled, antibody-opsonized RBCs (10⁹). At 3 hours after RBC injection, animals were killed, and spleen and liver cells were stained for CD68. (A) CD68⁺ spleen cells (macrophages, dendritic cells, and monocytes) are not yet significantly depleted within this 5-hour time frame. Data are presented as percentages of total spleen cells. (B) Liposomal clodronate uptake blocks subsequent ingestion of opsonized RBCs by macrophages. Only CD68⁺ spleen or liver cells are shown. The uptake of PKH-labeled liposomes and the uptake of DiD-labeled RBCs are indicated by fluorescence in their respective channels. Percentage values represent the mean percentages (± standard errors) of CD68⁺ cells that are positive for both liposomes (PKH) and RBCs (DiD). MFI indicates mean DiD fluorescence of cells positive for both liposomes and RBCs. Data presented are from 1 experiment representative of 3.