Effect of IL-12 on granuloma formation induced by injected Schistosoma japonicum eggs

The regulatory functions of IL-12 on granuloma formation by the eggs of S. japonicum in the lungs of BALB/c mice were studied. Mice were injected i.v. with the eggs to induce the pulmonary granuloma. On days 0, 1, 2, 3, 7, 8 after injection, mice were injected i.p. with murine rIL-12 at a dose of 1 microgram day-1 (Group I) or 3 micrograms day-1 (Group II) or with PBS as a control (Group III). On day 10, all mice were sacrificed. The areas of pulmonary granulomas in histological sections were quantitatively measured by image analyser and the levels of mRNA for IL-10, IFN-gamma, IL-12 and IL-5 were assayed by reverse transcriptase PCR (RT-PCR). The results showed that the mean area per granuloma was significantly decreased in Groups I and II as compared with Group III. As for cytokine induction, IL-10- and IFN-gamma-specific bands appeared in Groups I and II, but not in Group III. Bands for IL-5 appeared in all groups, while bands for IL-12 were not detected in any group. It is suggested that IL-12 could inhibit the Th2 dominant granuloma formation induced by the eggs of S. japonicum.