Isolation, preliminary characterization, and interferon antagonistic effect of a mammalian lectin-like substance

We have isolated from mouse costal cartilage a tissue antagonist of interferon (TAI) which accelerates the decay of an established antiviral state. The effect is reminiscent of substances previously isolated from the basement membrane of human amnion. Since we have recently shown that phytohemagglutinin can mimic the biological effect of TAI, we have explored the possibility that TAI could be an animal lectin-like material. First, TAI agglutinates mouse cells; second, this cell agglutination is inhibited by some sugars. Preliminary characterization indicates that the active molecule is a protein. After Sephadex G-100 gel filtration, TAI is found in a peak of 150,000 molecular weight. When purified by isoelectric focusing, this peak shows maximal activities corresponding to an isoelectric point of pH 8.8 TAI binds to polysaccharide residues of the cell membrane which could be its primary site of action, comparable to phytohemagglutinin.