To investigate the capture of OVA-liposome conjugates by macrophages, macrophage clone 39 was incubated for 30 min at 4uC or 37uC in the presence of fluorescence-labeled OVAliposome conjugates that contained a final concentration of 4 mg/ ml OVA. After the incubation, cells were washed with ice-cold PBS. In the case of using Alexa-labeled OVA-liposome conjugates, cells were then incubated with 1.2 mg/ml trypan-blue for 5 min at 4uC to block the fluorescence of Alexa-OVA attached to the cell surface. After the cells were washed, they were analyzed on a FACS Caliber flow cytometer (BD Bioscience). The histograms of fluorescence distribution were plotted as the number of cells versus fluorescence intensity on a logarithmic scale.