A conjugate consisting of keyhole-limpet hemocyanin (KLH) and fluorescein isothiocyanate (FITC) with potential immunostimulating activity. Vaccination with KLH-FITC may elicit an immune response against fluorescein and the production of anti-fluorescein IgG antibodies. KLH, a natural protein isolated from the marine mollusk keyhole limpet, is an immunostimulant carrier protein.