A fluorescent antibody is a laboratory tool used to detect specific proteins or antigens in cells or tissues. It involves attaching a fluorescent dye to an antibody that binds to the target antigen. When exposed to ultraviolet light, the dye emits a bright color, allowing researchers to visualize the presence and location of the antigen under a fluorescence microscope. This technique is widely used in immunology, pathology, and cell biology for diagnosing diseases, studying immune responses, and conducting research. By providing precise localization of proteins, fluorescent antibodies help scientists understand cellular functions and disease mechanisms more effectively.