Specific for fluorescein, FITC-labeled proteins. Reacts with both free and conjugated FITC, Kd = 1.5 x 10-8 M. Can be used for detection of FITC-labeled antigens or antibodies; capture antibody for FITC-labeled biopolymers. Can be used as enzyme-labeled second antibody for immunohistochemistry with FITC-conjugated mouse monoclonal antibodies.