A serial study of splenic reticuloendothelial system Fc receptor functional activity in systemic lupus erythematosus

A serial study of reticuloendothelial systems splenic Fc receptor function was undertaken in 13 patients with systemic lupus erythematosus (SLE). Fc receptor function was assessed by measuring the clearance half times of IgG-sensitized ⁵¹Cr labeled autologous erythrocytes from the circulation. Prolonged clearance half-times were initially detected in all patients, and the magnitude of the clearance defect was significantly correlated with disease activity (P <0.01, Spearman rank correlation) and immune complex levels (P <0.01). Clinical course and changes in receptor functional activity over time were found to be significantly correlated. Clearance half times tended to return to normal in all 11 patients who clinically improved. The clearance half time remained unchanged in 1 patient whose disease activity was stable, and it worsened in 1 patient whose illness flared. Levels of immune complexes also changed concordantly with clearance half times and disease activity. These studies underscore the interrelationship between the presence of circulating immune complexes, defects in Fc receptor function that might lead to prolonged circulation of these complexes, and disease activity in SLE.