Human splenic Fc receptor function and dysfunction: definition by circulatory clearance rate compared to computerized...

In vivo reticuloendothelial Fc receptor function was studied in 14 individuals. To assess this function Tc-99m-labeled IgG-coated autologous erythrocytes were injected intravenously and circulatory clearance rates of radioactivity were determined. In 12 individuals [6 normals and 6 patients with systemic lupus erythematosus (SLE)], kinetic computerized scintigraphic imaging of various internal organs was compared to circulatory clearance rates. Both circulatory clearance rates and percentage splenic uptake (PSU) were significantly depressed in patients. The difference between patients and normals was more significant for PSU than for circulatory clearance. Splenic uptake curves showed significantly less linearity for patients, suggesting that splenic defects in SLE are not only quantitative, but also are qualitative. Understanding the nature of immune clearance defects in immune complex mediated diseases may allow for a more rational approach to treatment of patients with these disorders.