The phagocytic activity assay was modified from the work of
Yoshida and Kitao [28]. 200 ml leukocyte suspensions
2 106 cells ml1 were spread on cover slips and incubated for 2 h.
The non-adherent cells were then removed by washing with RPMI
1640. 200 ml of fluorescence latex beads (Sigma) solution 2 107of
beads ml1 was added on each cover slip and incubated for 1.5 h at
room temperature. After incubation, the non-phagocyte beads
were washed with RPMI 1640. The cover slips were then fixed with
methanol and stained with Diff-Quick staining dye (Sigma) for 10 s.
Excessive stainwas removed by washing with PBS (pH 7.4), and the
number of phagocyte cells per 300 adhered cells was counted
microscopically. The phagocytic index (PI) was determined as follows:
PI ¼ Average number of beads per cell divided by the number
of phagocytizing cells.