Luciferase encoding λ phage particles either added directly to target cells (λ luc), or were preincubated with a gpD-specific rabbit antiserum (λ luc + gpD) prior to addition to target cells at a MOI of 106. In some cases, the parental (white bars) or FcγRI γ+ expressing (black bars) CV1 cells were preincubated with 5 µg/ml of a FcγRI ligand-binding blocking antibody, 10.1 (αFcγRI), or IgG1 isotype-matched control antibody (IgG1 isotype) for 30 minutes prior to the addition of λ(luc) or λ(luc) + αgpD. Forty-eight hours later, cells were harvested, and luciferase activity was measured in cell lysates. The results shown represent mean values calculated from triplicate samples; error bars represent the standard deviation. The data are representative of 3 independent experiments that yielded similar results. The asterisks (***) denote a statistically significant difference from control cells/conditions (p value < 0.001, one-way ANOVA).