ism of Rat Resistance to T. gondii larger than those from Lewis rats but much lower than these from BN rats. Our outcomes also showed that the iNOS expression level and NO concentration inside the peritoneal macrophages in the F1 progeny of BN6Lewis was considerably decrease than in Lewis rats, but larger than in BN rats. When contemplating the research on the Toxo1 locus, we note that the iNOS ge