Described herein are methods for assessing cytotoxicity of an agent. The methods include providing a target cell that has been engineered to express intracellularly a reporter that is not expressed endogenously by the target cell, exposing the target cell to an agent capable of modulating cytotoxicity and assaying the activity of the reporter, wherein a change in reporter activity relative to a reference value is indicative of the agent being able to modulate cytotoxicity of the target cell.