In contrast, with PEM that express Perforin-2, the inhibition of endogenous ROS by NAC enables S. typhimurium to replicate significantly more than mock treatment during the first 4 hr after infection, suggesting that ROS in combination with Perforin-2 helps to restrain S. typhimurium replication during this period (Figure 2A). The gene discussed is MPEG1; the disease is infection.