Secondary antibodies are designed to bind to primary antibodies to aid in detecting, measuring, sorting, and studying antigens of interest in various immunoassays including ELISA, Western Blot, and immunofluorescence. Indirect immunofluorescence assays using secondary antibodies offer several advantages over direct immunofluorescence methods. They have greater sensitivity, flexibility, versatility, and diversity, and also offer the ability to perform multi-labeling or multiplexing in experiments. The same secondary antibody can be used across multiple applications for validating target antigen detection.