Neutropenia augments experimentally induced Schistosoma japonicum egg granuloma formation in CBA mice, but not in C57BL/6 mice

The present study was designed to investigate the role of neutrophils during the development of Schistosoma japonicum egg granulomas, in C57BL/6 and CBA mice. Laid eggs were implanted into the liver and monoclonal antibody, RB6-8C5, was used to eliminate neutrophils. After daily antibody treatment between days 9 and 13 of egg implantation, both strains of mice showed a marked decrease in neutrophil infiltration and coagulative hepatocyte necrosis at 2 weeks. At 4 weeks, after antibody administration every other day between days 16 and 26, granuloma formation in C57BL/6 mice was not affected by the treatment, whereas CBA mice exhibited a significant increase of reactions. Neutropenia augmented the Th2 cytokine response (IL-4, IL-13 and IL-5), but not for IFN-gamma at any time point examined and in either strain of mice. Higher levels of IL-4 and IL-13 were noted in CBA mice at early and late stages of granuloma formation, compared to C57BL/6 mice. There was also a striking difference in IL-13 production between the two strains. Our results indicate that neutropenia is associated with a significant augmentation of S. japonicum egg-induced granuloma formation in CBA mice, probably through increase in Th2 cytokines, however, the effects differ between early and late stages and between high and low responders.