Activated human PMN synthesize and release a strongly fucosylated glycoform of  1 -acid glycoprotein, which is transiently deposited in human myocardial infarction Dennis C. W. Poland,* Juan-Jesu ´ s Garcı ´a Vallejo,* Hans W. M. Niessen, †,‡,§ Remco Nijmeyer, †,‡,§ Jero Calafat, ¶ C. Erik Hack, ‡,§, Bert Van het Hof,* and Willem Van Dijk* ,1 Departments of *Molecular Cell Biology & Immunology, Glycoimmunology Group, † Pathology, and ‡ Clinical Chemistry, and § Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, the Netherlands; ¶ Division of Cell Biology, the Netherlands Cancer Institute, Amsterdam; and  Department of Immunopathology, Sanquin Research at CLB and Laboratory for Experimental and Clinical Immunology, Academic Medical Center, University of Amsterdam, the Netherlands Abstract:  1 -Acid glycoprotein (AGP) is a major acute-phase protein present in human plasma as well as in polymorphonuclear leukocytes (PMN). In this report, we show that PMN synthesize a specific glycoform of AGP, which is stored in the specific and azurophilic granules. Activation of PMN re- sults in the rapid release of soluble AGP. PMN AGP exhibits a substantially higher apparent molecular weight than plasma AGP (50 – 60 kD vs. 40 – 43 kD), owing to the presence of strongly fucosylated and sialylated polylactosamine units on its five N- linked glycans. PMN AGP is also released in vivo from activated PMN, as appeared from studies us- ing well-characterized myocard slices of patients that had died within 2 weeks after an acute myo- cardial infarction. AGP was found deposited tran- siently on damaged cardiomyocytes in areas with infiltrating PMN only. It is interesting that this was inversely related to the deposition of activated complement C3. Strongly fucosylated and sialy- lated AGP glycoforms have the ability to bind to E-selectin and to inhibit complement activation. We suggest that AGP glycoforms in PMN provide an endogenous feedback-inhibitory response to ex- cessive inflammation. J. Leukoc. Biol. 77: 000 – 000; 2005. Key Words: activated complement C3  molecular weight  oroso- mucoid  subcellular localization  secretion  specific granules  azurophilic granules INTRODUCTION The acute-phase response involves local and systemic reac- tions, which serve to limit tissue damage and to restore ho- meostasis after infection or tissue injury [1, 2]. The influx of polymorphonuclear cells (PMN) into inflamed tissues is one of the early, local responses, a P- and E-selectin-dependent pro- cess [3, 4]. PMN are equipped with a broad range of com- pounds that are stored in various types of granules [5]. These compounds are rapidly released from PMN once infiltrated into the inflamed area and serve to assist in the combat against pathogens and the removal of damaged cells. Complement activation fragments are formed in the inflamed area, such as C5a, and direct the infiltration of PMN. These fragments are supposed to promote ongoing tissue damage by stimulating the infiltration and activation of PMN [6]. One of the systemic inflammatory reactions is the hepatic acute-phase response, which involves the increased synthesis of a set of serum proteins with anti-inflammatory properties, the acute-phase proteins [1, 2, 7, 8]. It is assumed that the function of these proteins is to dampen the side-effects of the local inflammatory reactions and to prevent a progression to chronic inflammation [2], although some acute-phase proteins may stimulate inflam- mation and tissue damage as well [9].  1 -Acid glycoprotein (AGP), also known as orosomucoid, is one of the major acute- phase glycoproteins. Human plasma AGP contains five N- linked complex-type glycans, which are strongly sialylated and comprise about half of its molecular mass [10, 11]. The hepatic acute-phase response induces an increased 3-fucosylation of these glycans, resulting in the occurrence of AGP glycoforms rich in sialyl Lewis x groups in plasma during inflammation [12]. It is interesting that these AGP glycoforms, by binding to E-selectin [13] and by amelioration of complement-induced damage [14], possibly counteract the influx of PMN in inflamed tissue. Most acute-phase proteins are produced in the liver. It is remarkable that a number of acute-phase proteins are also present in resting PMN [15–18]. AGP is one of them; a mem- brane-associated as well as an intracellular-localized form has been described for PMN [15, 17]. The glycosylation process in PMN gives rise to polyfucosylated and sialyl Lewis x -expressing glycans on its cell-surface glycoproteins, which may constitute specific ligands for E- and P-selectin [19, 20]. AGP produced 1 Correspondence: Glycoimmunology Group, Department of Molecular Cell Biology & Immunology, VU University Medical Center, Van der Boechorst- straat 7, P.O. Box 7057, 1007 MB Amsterdam, the Netherlands. E-mail: w.vandijk@vumc.nl Received October 6, 2004; accepted December 9, 2004; doi: 10.1189/ jlb.1004566 0741-5400/05/0077-0001 © Society for Leukocyte Biology Journal of Leukocyte Biology Volume 77, April 2005 1 Uncorrected Version. Published on January 12, 2005 as DOI:10.1189/jlb.1004566 Copyright 2005 by The Society for Leukocyte Biology.