Concentration-dependent restoration of phagocytosis of EIgG by sphingosine-treated nonprimed (A) and fMLP-primed (B) PMN in the presence of DiC10. PMN (2 × 10⁶/mL) were preincubated with different concentrations of sphingosine for 30 minutes at 22°C and washed twice, and then the PMN were incubated with DiC10 at different concentrations at 22°C for 30 minutes. The PMN were then challenged with EIgG (A) or primed with fMLP (10⁻⁷ mol/L) and then EIgG (B). The control phagocytic index was 16.4 ± 2.4 (100% control) in nonprimed cells and was 59.2 ± 8 in fMLP-primed PMN. The values represent the mean ± SD for three experiments. Comparisons were made between DiC10 versus cells not treated with DiC10: ***P < .0001, **P < .001, *P < .005.