J. Cell Sd. 59, 245-256 (1983) 245 Printed in Great Britain © Company of Biologists 1983 HYPERIMMUNE HUMAN ABO BLOOD-TYPING SERA: REACTIVITY WITH MURINE LAMININ AND CYTOTOXICITY FOR METASTATIC MURINE TUMOUR CELLS J. P. McCOY*, D. SCHRIERf, E. J. LOVETT, W. J. JUDD AND J. VARANI Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan 48109, U.SA. SUMMARY Commercially prepared ABO blood-typing antisera have been tested for their ability to bind to murine laminin and their cytotoxic effects upon high and low metastatic variants of a murine fibrosarcoma. Previous studies have shown that a-D-galactopyranosyl end-groups comprise the major antigenic determinants on type B erythrocytes and that these same end-groups are present on murine laminin purified from the EHS sarcoma and on a laminin-like glycoprotein on the surface of the high, but not low, metastatic fibrosarcoma cells. In the present study we found that all sera containing anti-B activity were cytotoxic to the high, but not the low, metastatic cells and that all of these sera reacted strongly against immobilized murine laminin in an enzyme-linked immunosor- bent assay. Sera lacking anti-B activity, i.e. anti-A antisera, were much less cytotoxic to either cell line and three of the four anti-A sera did not bind to murine laminin. The laminin reactivity and cytotoxic effect of the anti-B sera were specifically abrogated by preincubation of the sera with water- soluble blood group B substance or with murine laminin but not with water-soluble blood group A substance. INTRODUCTION Terminal a-D-galactopyranosyl groups are known to be a major constituent of human type B blood group antigen (Watkins, 1966). It is not surprising, therefore, that isolectin B 4 from Griffonia simplicifolia (GSI-B 4 ), which has specificity for a-D- galactopyranosyl groups, binds to human type B erythrocytes but not to type A or O cells (Murphy & Goldstein, 1977). It has recently been reported that murine laminin also binds this lectin (Shibata et al. 1982), suggesting that this glycoprotein also contains a-D-galactopyranosyl groups as part of its carbohydrate structure. In the light of these observations and in the light of the fact that antibodies to the major blood group antigens are directed to the carbohydrate structure (Kabat & Leskowitz, 1955), we predicted that human serum with anti-B specificity would cross-react with murine laminin. •Author for correspondence. tPresent address: Warner Lambcrt-Parke Davis, 2800 Plymouth Rd, Ann Arbor, MI 48105, U.S.A.