Immune complex formation during Plasmodium berghei infection of OF1 mice was investigated. Circulating immune complexes (CIC) were detected by the Clq-binding assay and the conglutinin-binding solid-phase assay in lethal or drug-limited infections. CIC appeared on day 9 of infection, peaked on day 11, and disappeared only after complete cure of the infection. Analysis of the immune complexes detected by the Clq-binding assay revealed the following characteristics: sedimentation coefficients of 13S to 21S, resistance to DNAse, and selective removal by filtration through protein A bound to Sepharose. Glomerular deposits of IgM preceded the appearance of CIC, whereas deposits of IgG and C3 were concomitant with the appearance of CIC. Tissue-bound immunoglobulins were also found in the choroid plexus. The appearance of anti-malarial antibodies and malarial antigens in the serum was closely associated with a depression of C3 levels and the presence of CIC. Drug treatment was followed by normalization of C3 levels, and clearance of both CIC and malarial antigens.
This work was supported by WHO, the UNDP/World Bank/WHO Special Program for Research and Training in Tropical Diseases, the Swiss National Foundation (Grant 3.847.0.77), and the Dubois-Ferriere Dinu Lipatti Foundation.