Plasmodium berghei malaria: blockage by immune complexes of macrophage receptors for opsonized plasmodia

Immune complexes produced in vitro by mixing immune serum and soluble Plasmodium berghei antigens and immune complexes precipitated from serum of acutely infected rats blocked macrophage receptor sites for opsonized plasmodia. The immune complexes were precipitated from acute-phase serum, using polyethylene glycol, and their composition was determined by using a Raji cell immunofluorescence assay. The immune complexes contained immunoglobulin G (IgG), IgM, and malarial antigens. These results indicate that immune complexes in the serum of acutely infected animals may protect the plasmodia from the activities of macrophages.