FCGR3B CN is proportional to gene expression and function in the normal population. Surface expression of FcγRIIIb increases with increasing FCGR3B CN. (A) Flow cytometry plot of neutrophils stained with PE-labeled anti-FcγRIIIb in one experiment that is representative of three. (B) Expression of FcγRIIIb (geometric mean fluorescence normalized in three separate experiments to the mean of intermediate CN individuals) correlates with gene dosage of FCGR3B. P value refers to one-way ANOVA with a post test for linear trend. The horizontal bar indicates the mean. (C) Neutrophil adhesion to IgG-coated glass slides after 4 min of flow at a shear stress of 0.1 Pa in an individual with low FCGR3B compared with that of an individual with high FCGR3B. Bar, 20 μm. (D) Neutrophil adhesion to bound IgG under flow conditions increases with FCGR3B CN (after 4 min of flow at a shear stress of 0.1 Pa) in two experiments, which were pooled. P value refers to one-way ANOVA with a post test for linear trend. The horizontal bar indicates the mean. (E) Uptake of immune complexes in individuals with low, intermediate, or high FCGR3B. Percentages of neutrophils positive for FL4 after 10 min incubation with antibody-opsonized, Alexafluor-labeled ovalbumin at 37°C are greater in individuals with more FCGR3B. Mean and SEM are shown for three to six individuals per group from two experiments. P value from nonparametric one way ANOVA (Kruskal-Wallis test).