A novel carbohydrate-glycosphingolipid interaction between a beta-(1-3)-glucan immunomodulator, PGG-glucan, and lactosylceramide of human leukocytes.
The immunomodulator Betafectin(R) PGG-glucan is a homopolymer of glucose derived from yeast cell walls which has been demonstrated to enhance leukocyte anti-infective activity in vitro and in vivo, without the induction of proinflammatory cytokines. We report here the purification of a PGG-glucan-binding element from human leukocytes and its identification as lactosylceramide, a major glycosphingolipid of neutrophils, which includes the CDw17 epitope. The binding of radiolabeled PGG-glucan to purified lactosylceramide was saturable, specific, and time- and temperature-dependent. Lactosylceramides from human leukocytes were fractionated by high performance liquid chromatography in order to analyze the effect of ceramide structure on binding. A variety of fatty acid chain lengths with varying degrees of unsaturation were found to support binding to radiolabeled PGG-glucan. However, DL-lactosylceramides containing dihydrosphingosine did not bind. Radiolabeled PGG-glucan bound several other neutral glycosphingolipids with a terminal galactose, including galactosylceramide, globotriaosylceramide, and gangliotetraosylceramide. The binding of radiolabeled PGG-glucan to lactosylceramide was not inhibited by glycogen, dextran, mannan, pustulan, laminarin, or a low molecular weight beta-(1-3)-glucan, but was inhibited by high molecular weight beta-(1-3)-glucans and by a monoclonal antibody to lactosylceramide. Although this glycosphingolipid has been shown in numerous reports to bind various microorganisms, this represents the first report of lactosylceramide binding to a macromolecular carbohydrate.
Zimmerman
J W
JW
Alpha-Beta Technology, Inc., Worcester, Massachusetts 01605, USA. jzimme@abti.com
Lindermuth
J
J
Fish
P A
PA
Palace
G P
GP
Stevenson
T T
TT
DeMong
D E
DE
D000276:Adjuvants, Immunologic / Q000378:metabolism*; D015703:Antigens, CD / Q000378:metabolism; D001665:Binding Sites; D002454:Cell Differentiation; D005936:Glucans / Q000378:metabolism*; D006028:Glycosphingolipids / Q000378:metabolism*; D006801:Humans; D007790:Lactosylceramides / Q000378:metabolism*; D007962:Leukocytes / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D047071:beta-Glucans
D000276:Adjuvants, Immunologic; D015703:Antigens, CD; D005936:Glucans; D006028:Glycosphingolipids; D007790:Lactosylceramides; D047071:beta-Glucans; C069894:poly-1-6-glucopyranosyl-1-3-glucopyranose glucan; C009744:CDw17 antigen