Clearance of ⁵¹Cr-labeled SRBC from the circulation after in vivo Ad-mediated FcγRIIA cDNA gene transfer. Sprague-Dawley rats were administered AdFcγRIIA or AdNull intravenously (10⁹ pfu). After 48 hours,⁵¹Cr-labeled opsonized (IgG-coated) RRBC or nonopsonized RRBC as controls were injected intravenously. At 5 to 120 minutes, blood samples were collected and ⁵¹Cr-radioactivity measured using a gamma scintillation counter. The level of⁵¹Cr-RRBC in the blood was expressed as a percentage of the value obtained at 5 minutes (100%) after injection. (A) Clearance of nonopsonized RRBC. Control, no vector administered (○); AdNull (□); AdFcγRIIA (▵). Each point represents the mean and standard error from 3 animals in each group. (B) Clearance of opsonized RRBC. The symbols are identical to those used in (A). Each point represents mean and standard error from 14 animals in control group, 12 animals in group infected with AdNull, and 17 animals infected with AdFcγRIIA.