Leukocyte surface origin of human alpha1-acid glycoprotein (orosomucoid).

Abstract

Specific antibodies against human .alpha.1-acid glycoprotein reacted with human lymphocytes, granulocytes and monocytes. The antigen on the leukocytes is an externally located integral membrane glycoprotein which is made by the cells and has an apparent MW of 52,000. It is released from cells in vitro to the culture medium. The MW of the soluble fragment is 41,000, which corresponds to that of .alpha.1-acid glycoprotein in serum and urine. Peptide mapping confirmed that the main part of the cellular membrane antigen consists of .alpha.1-acid glycoprotein with an additional, probably hydrophobic fragment. This finding may partially explain the increase in the serum levels of .alpha.1-acid glycoprotein observed in many disorders involving leukocyte proliferation. The known sequence homology of .alpha.1-acid glycoprotein with immunoglobulins can now be more easily understood by their origin in similar cell types.