Localization of eosinophil major basic protein onto eggs of Schistosoma mansoni in human pathologic tissue

The eosinophil granule major basic protein (MBP), constituting the core of the granule, is toxic to helminths and mammalian cells in vitro. To determine whether eosinophil degranulation and extracellular MBP deposition occur in schistosomal lesions in human tissues, the authors performed an indirect immunofluorescence assay on sections of formalin-fixed, paraffin-embedded specimens from patients infected with Schistosoma mansoni. A total of 8 liver and 4 colon specimens from 12 patients were examined. In the liver, 22 eggs were observed; only 3 of these were not confined to granulomas, and none of these 3 demonstrated extracellular MBP deposition in close proximity to the eggs. The remaining 19 eggs were confined to granulomas and 12 showed extracellular MBP deposition either on the surface of or in close proximity to the eggs. In the colon, 90 eggs were observed; 87 were not confined to granulomas, and none of these had MBP deposited on them. The remaining three eggs were confined to granulomas and only one showed MBP deposition. Finally, intense extracellular MBP deposition was noted in granulomas in association with the Splendore-Hoeppli phenomenon. The results show that the helminthotoxic MBP is deposited on eggs in granulomas in human tissues and suggest that the Splendore-Hoeppli phenomenon is accounted for in part by deposition of eosinophil granule MBP.