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We investigated the kinetics of parasite replication, leukocyte migration, and cytokine/chemokine mRNA expression in the heart tissue from animals infected with the Colombiana strain of Trypanosomacruzi. Cardiac tissue parasitism was noticeable at 15 days, peaked around 30 days and was dramatically reduced at 120 days postinfection (p.i.). Kinetic studies showed that the inflammatory infiltrate was dominated by the presence of αβT CD3⁺ CD4⁺ CD8^–, αβT CD3⁺ CD4^–CD8⁺ lymphocytes and macrophages. The mRNA expression of the monokines IL-1β and IL-12(p40) was elevated at 15 days p.i. and controlled at later time points. In contrast, TNF-α mRNA was expressed throughout the infection. Interestingly, we found that at 15 and 30 days p.i. cytokine expression was dominated by the presence of IFN-γ mRNA, whereas at 60 days or later time points the balance of type 1 and type 2 cytokines was switched in …