Murine Schistosomiasis mansoni: anti-schistosomula antibodies and the IgG subclasses involved in the complement- and eosinophilmediated killing of schistosomula in vitro

Abstract

Summary Protein A-sepharose affinity chromatography was used to isolate IgG subclasses from the serum of CBA mice chronically infected with Schistosoma mansoni. The subclasses were tested for the presence of two antibodies which are responsible for the death of young schistosomula in vitro; ‘lethal antibody’ (LA), which kills schistosomula in co-operation with complement and ‘eosinophil adherence antibody’ (EAA) which causes the death of schistosomula by promoting the adherence of eosinophils to the parasite. LA and EAA were detected only in the IgG fraction of the serum. LA was concentrated in the IgG_2a fraction and EAA in the IgG₁ fraction. The development of IgG subclasses specific for schistosomula was followed in mice exposed to twenty cercariae by the fluorescent antibody technique. IgG₁, IgG_2a and IgG_2b antibodies were detected 2 weeks after infection and their titres rose steadily to reach high levels by weeks 12 or 14. IgM antibody was not detected until week 6 and IgA until week 10; both were present at lower concentrations than the IgG₁ antibodies.