Opsonic properties of C-reactive protein in vivo

The capacity of CRP to alter the clearance and site of sequestration of erythrocytes was examined. Mouse erythrocytes, coated with PnC to provide a binding site for CRP, were radiolabeled and injected into homologous mice. The liver, spleen, kidneys, and lungs were removed and counted to assess the site of erythrocyte clearance. In the presence of CRP, an increase in splenic sequestration of E-PnC was observed along with a slight decrease in hepatic sequestration. This altered clearance pattern was dependent on both C activation and on the continued presence of CRP. The clearance of cells coated with IgM or IgG antibody to PnC was compared. In both cases, antibody caused an increase in sequestration by the spleen. However, IgM-coated cells required C for splenic clearance, whereas IgG-coated cells did not. We have shown in these experiments that CRP can affect the in vivo pattern of organ sequestration of cells to which it is bound in a manner similar to antibody.