Synergistic effect of H₂O₂ and PMA on activation of the LTR. The reaction mixture contained 2 × 10⁶ Jurkat LTR_luc and, where indicated, 100 ng/mL PMA, 100 U/mL TNF-, 100 U/mL IL-2, and H₂O₂ at the concentrations indicated in RPMI at a final volume of 2.0 mL. The effect of PMA, TNF-, or IL-2 alone is indicated by the (○) at zero H₂O₂concentration. The results are the mean ± SEM of four to six experiments. The asterisk indicates a significantly greater effect of a combination of PMA (or TNF- or IL-2) and H₂O₂ than the additive effect of each alone (P < .05).