Abstract: The invention relates to a novel non-radioactive method to detect cytolytic activity that provides a measure of the existence and magnitude of an immune response against a particular antigen or immunogen. Provided is a method for detecting cytolytic activity of cells or a substance against a population of target cells, comprising the steps of providing target cells with a first nucleic acid sequence encoding a reporter molecule and a second nucleic acid sequence encoding an antigen of interest; co-culturing the target cells with a sample containing cells or a substance suspected of having cytolytic activity; and detecting the viability of target cells provided with the reporter molecule. Also provided are a kit and a nucleic acid for use in a method according to the invention.