MD-2 enhances opsonophagocytosis. (A) Adherent pMφ, RAW macrophages, or PBMCs were infected for 30 minutes with untreated (▩) or MD-2^6xHis–opsonized (20 ng/mL; ■) fluorescent protein expressing live Nm and Yp. Shown is the average fluorescence of triplicate wells plus SD. Fluorescence units were plotted on an arbitrary scale (AFU), and cellular autofluorescence (□) was set to 0 (phagocytic index). (B) RAW macrophages or mouse pMφ were incubated with YFP-Yp as in panel A and were subjected to confocal microscopy. Nuclei were stained with Hoescht 33258 (blue), and the cell surface was stained with an α-CD11b (red). Magnification 40×.