Stabilin-1– or stabilin-2–expressing cells significantly enhance PS-bead engulfment by macrophages. (A) Phagocytosis assays were performed in a coculture of P388D1 and L cells expressing empty vector, stabilin-1, or stabilin-2. P388D1 cells were seeded on BMQC-labeled L-cell transfectants, and the next day, NBD-PC–labeled PS-coated beads were added to the coculture of P388D1 and L-cell transfectants. After incubation for 1 hour, engulfment of damaged RBCs by P388D1 cells (Q4 regions) was quantified by FACS analysis. Percentages of phagocytosis for P388D1 alone and in coculture with L/Mock cells were 12.2% ± 3.9% and 13.0% ± 2.0%, respectively, whereas in the presence of L/Stab-1 or L/Stab-2 cells phagocytic activity of P388D1 cells was increased by 36.6% ± 5.7% and 36.6% ± 2.3%, respectively. A representative result is shown. (B) Phagocytosis assays were performed in a coculture of P388D1 and L cells expressing empty vector, stabilin-1, or stabilin-2. Data represent mean ± SD from at least 3 experiments; t test: *P < .01 versus L/Mock. (C) DIC images from supplemental Video 1 show the engulfment of PS bead (arrowheads) by P388D1 cells in coculture. The gray dotted lines indicate the boundary of HSECs.