In conclusion, with the iNOS-KO rat model, the results reveal that iNOS plays a critical role in the regulation of immune system reactivity, particularly in Th1/Th2-associated cytokine responses and chemokine production in rats, during S. japonicum infection, which leads to a rapid rejection of schistosome survival and no granuloma formation. The gene discussed is NOS2; the disease is Granuloma.