The galactophilic lectin expressed on the surface of cultured Hodgkin's cells, recently described by this laboratory, has binding characteristics similar to those of the hepatic asialoglycoprotein receptor (HBP), and has been recognized as a Mr 55,000 (p55) membrane glycoprotein by a polyclonal antiserum to rat HBP. This study confirms the close structural relationship between the two lectins showing immunological cross-reactivity of monoclonal and polyclonal antibodies recognizing distinct epitopes on rat or human HBP. In support of the suggested dual nature of p55 as lectin and ectosialyltransferase, enzyme activity is inhibited by the monoclonal anti-HBP antibody, anti-HA 116. Cultured Hodgkin's cells, as purified HBP, agglutinate T-lymphocytes expressing hyposialylated membrane glycosyl determinants. This cell-cell interaction mediated by p55 results in the incorporation of sialic acid into lymphocyte surface asialo-glycans. The function of the Hodgkin's lectin as lymphocyte agglutinant in vitro suggests its role as an immunomodulator contributing to the immunodeficiencies associated with Hodgkin's disease.

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Supported in part by Grant P30CA13330 awarded by the National Cancer Institute, Department of Health and Human Services, by a grant from the Chemotherapy Research Foundation, by a grant from the Henry M. and Lillian Stratton Foundation, Inc., and by NIH Grants AM17702, AM32972, and GM29133.

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