Plasmodium berghei yoelii infection in mice suppressed granuloma formation around Schistosoma mansoni eggs in the lungs. This suppressive effect was observed as early as 4 days after schistosome eggs were injected into malaria-infected mice and the maximum suppressive effect was seen by the 16th day. At that time granulomas in control mice were 58% larger than those observed in marlaria-infected mice. In addition, granuloma formation was found more consistently in control mice than in mice infected with malaria. These data suggest that malaria has a direct influence on an immunologic reaction of the delayed hypersensitivity type. There was no significant difference in the level of antibodies, specific for schistosome eggs, in the sera of the malaria-infected mice as compared to mice injected with S. mansoni eggs alone.
On leave of absence from the Tropical Research Institute, Cairo.