2.4. Phagocytosis assay
AM (0.25 106) in RPMI were incubated at 37°C in a
humidified atmosphere of 5% CO2 in well chamber slides
(Lab-Tek 11 Chamber slide w/cover, Nalgene Nunc International)
for 3 hr for adherence. The non-adherent cells
were then washed off and 200 uL fresh medium (RPMI-
1640 containing 10% FCS) was added. The assay for phagocytosis
was performed by adding latex beads to the wells in
a ratio of 10 beads/cell and continuing the incubation for
another 1h at 37°C. Phagocytosis was terminated by washing
the wells 5 times with RPMI with 10% FCS. The slides
were stained with Hemastaining kit (Hema 3 stain set,
Fisher Scientific). The percentage of infected cells and the
phagocytic index (number of beads per infected cell) were determined
by microscopic examination under the oil immersion.