Lectin activity as a marker for Hodgkin disease cells

Abstract

Treatment of cultured Hodgkin disease (HD) cells with neuraminidase results in decreased reactivity of monoclonal antibody VIM-D5 with its antigen, the X hapten, a fucosyl-N-acetyllactosamine. The other feature characteristic of HD cells is the expression of high levels of ectosialyltransferase activity. We present evidence for a cause-effect relationship between these two findings in that VIM-D5 antigenicity can be restored on neuraminidase-treated HD cells by modulating transferase activity. This can be interpreted in terms of a lectin activity of the ectosialyltransferase that binds the X hapten's desialylated galactosyl residues, thereby preventing antigen recognition by VIM-D5 antibody. This proposed mechanism is indistinguishable from the autoinhibition phenomenon described for another galactophilic binding protein, the hepatic binding protein (HBP), which binds its own terminal galactosyl residues following neuraminidase treatment. We establish a close relationship between the HD galactophilic binding site and HBP in that antiserum to HBP (i) inhibits the neuraminidase-induced loss of VIM-D5 antigenicity, (ii) blocks the binding of asialoglycoprotein to hepatocytes after being absorbed by and eluted from HD cells, and (iii) recognizes a single HD protein, which in its high level of expression is unique to HD cells. The presence of lectin activity in its classic sense on the surface of HD cells is confirmed by the erythrocyte-agglutinating ability of these cells. This lectin activity, which appears to be related to an ectosialyltransferase on the surface of HD cells, may serve as a marker for the abnormal cells characteristic of HD.