CD4 and infection: In a recent pilot study of a sequential combined treatment with allopurinol and benznidazole in the chronic phase of Trypanosoma cruzi infection (Pérez-Mazliah et al., 2012), we have observed that the frequency of peripheral naïve CD4+ and CD8+ T cells, that are generally diminished in this phase of the infection (Albareda et al., 2006, 2009), is improved along with a decrease in the frequency of peripheral CD4+ and CD8+ T cells expressing the activation marker HLA-DR after completion of allopurinol administration.