Inflammation-induced expression of sialyl Lewisx is not restricted to α1-acid glycoprotein but also occurs to a lesser extent on α1-antichymotrypsin and haptoglobin

Abstract

Acute and chronic inflammation-induced expression of sialyl Lewisx has already been shown to occur on α1-acid glycoprotein. We now demonstrate that this phenomenon is not restricted to α1-acid glycoprotein but also occurs on two other acute-phase proteins. ie on α-antichymotrypsin and on haptoglobin. The level of expression of sialyl Lewisx on these proteins was lower than on α1-acid glycoprotein, in all likelihood because α1-acid glycoprotein is the only acute-phase protein containing tetraantennary glycans. No expression of sialyl Lewisx was detectable on α1-protease inhibitor, a protein with a high diantennary glycan content. Non-sialylated Lewisx was not detectable on these major acute-phase proteins in any of the conditions studied. This indicates that the majority of the α3-linked fucose residues are present as sialyl Lewisx on α1-acid glycoprotein, α1-antichymotrypsin and haptoglobin. The absolute contribution to the total phenotype in plasma of protein containing this determinant in a multivalent form was highest for α1-acid glycoprotein. This leads us to propose that α1-acid glycoprotein is, among the acute-phase proteins studied, the one with the highest potential for interference with the extravasation of leukocytes by binding to the selectins.