Our results demonstrated that children with leukemia were more likely to be infected with T. gondii when compared with healthy controls (16.8% vs 9.7%, P = 0.002), though there was no significant difference between children with leukemia and controls with regard to the level of IgM antibodies, which was consistent with previous studies (Gharavi, Roozbehani & Mandeh, 2017). The gene discussed is CD40LG; the disease is leukemia.