Novel antigenic specificity involving the blood group antigen, Lea, in combination with onco-developmental antigen, SSEA-1, recognized by two monoclonal antibodies to human milk-fat globule membranes.

Two monoclonal antibodies to human milk-fat globule membranes, which recognize an epithelial antigen designated MAM-3c, were found to bind strongly to epithelial glycoproteins derived from non-secretors. Further investigations, using purified glycoproteins and structurally defined oligosaccharides, established that the optimal antigenic structure for both antibodies involves the Type 1 based blood group antigen, Lea, in combination with the Type 2 based onco-developmental antigen, SSEA-1, (Formula: see text) as in lacto-N-difucohexaose II. The antibodies may also react with the corresponding monofucosyl structures lacking the 3- or 4- linked fucose residues and to a lesser extent with the afucosyl tetrasaccharide sequence as in lacto-N-tetraose. The Lea and SSEA-1 antigens are known to occur on human epithelial glycoproteins. However, this is the first report of an antigenic specificity involving a combination of the Type 1 and Type 2 based fuco-oligosaccharides and occurring on epithelial glycoproteins.