Multiple proteins related to the soluble galactose-binding animal lectin revealed by a monoclonal anti-lectin antibody.

A monoclonal antibody (NIBy 142-36/8) raised against the soluble galactose-binding lectin of bovine heart muscle has been tested by solid-phase vinyl-plate radiobinding and nitrocellulose immunoblotting with homogenates of various bovine tissues, and the muscle tissues of pig, rabbit, chicken and rat. Muscle lectins of chicken, rabbit and rat differed from those of man and pig in their lack of reactivity with the 36/8 antibody. There was a good correlation of haemagglutinating activities and immunoreactivities of the bovine tissue homogenates, suggesting that the soluble galactose-binding protein is a major haemagglutinin in various tissues. Immunoblotting experiments revealed an array of antigenically active components in the homogenates in addition to the 13 and 26kDa proteins that were previously detected in preparations of purified lectin. These were in the range 36kDa to more than 200kDa, and a different spectrum of immunoreactive components was found in various cell types. Galactose-binding activity was demonstrable in 13, 26 and 36kDa components in certain bovine tissues, suggesting that the immunoreactive components of higher Mr may be inactive precursor forms of the lectin.