Indeed, clinical studies by Vitelli-Avelar et al. (2008), Fiuza et al. (2009), and de Araújo et al. (2011, 2012) found that individuals in the indeterminate clinical form of the disease have a higher frequency of CD4+CD25high T cells population secreting IL-10 and expressing FOXP3, indicating that the balance between regulatory and effector T cells might be a critical determinant of disease progression in Chagas disease [26–29]. This evidence concerns the gene IL10 and Chagas disease.