Chickens were immunized with purified ?-Galactosidase (lacZ) protein emulsified in Freund’s adjuvants. After multiple injections, eggs were collected from the hens, IgY fractions were prepared from the yolks, and then affinity-purified antibodies were prepared using ?-Galactosidase conjugated to an agarose matrix. The final product is a mixture of both affinity-purified antibodies (25 μg/ml) and purified IgY (10 mg/ml), and is filter-sterilized.