Dynamics of M1 and M2-specific enzyme expression in macrophages during S. japonicum infection. Peritoneal macrophages were purified from normal or S. japonicum infected mice at indicated time points. Expression of iNOS (A) and Arg-1 (B) mRNA was evaluated by real-time PCR. Transcript levels for each enzyme in macrophages are expressed as fold change over transcript levels in macrophage from normal mice (0 week). Data are expressed as the mean ± SD of three independent experiments with 6 mice per group in each experiment.