FIG. 4.

Effect of T. cruzi infection on apoptosis of H9c2 cardiac cells. A. H9c2 cells were plated on coverslips and infected with T. cruzi; TNF treatment followed infection by 24 h. Cultures of H9c2 cells underwent TUNEL labeling and immunofluorescence for T. cruzi. Cells were counted for infection and TUNEL positivity. B. H9c2 cells were infected at either 37°C or 20°C for 2 h, treated with TNF-α, and assessed for apoptosis via annexin V-FITC and FACS analysis 24 h after TNF-α treatment. C. T. cruzi infection was identified via a polyclonal anti-T. cruzi antibody and calculated per 300 cells for infection occurring at both 37°C and 20°C. Data represent means of three experiments plus standard deviations of the means. Significant variation from untreated control cells (C) or from the 37°C temperature of infection (panel C) (P < 0.05) is designated by an asterisk (*). Significant variation from uninfected, TNF-α-treated cells is designated by a pound sign (#).