The THP1 cells are treated with 40ng/ml of PMA for overnight to differentiate them into macrophages. The medium containing PMA was removed and fresh media was added to the cells. The cells were then treated with a recombinant protein which has the potential to downregulate ROS. We observed this activity till 24hrs. Also we observed that there was a time-dependent increase in untreated PMA-differentiated cells. Is it possible or any study reported for such long-term activation after PMA removal? Please suggest any positive control for this study.