SIALYLATED O-GLYCANS AND L-SELECTIN SEQUENTIALLY MEDIATE MYELOID CELLROLLING IN-VIVO

Leukocyte rolling precedes firm adhesion and emigration in inflammator y cell recruitment. Both P-selectin, an endothelial lectin that binds to sialylated O-glycans containing sialyl-Lewis(x) (sLe(x)) on the gra nulocyte surface, and leukocyte L-selectin have been shown to mediate leukocyte rolling in vivo. Here, we investigate rolling of isolated hu man neutrophils (PMN), HL-60 promyelocytes, and an L-selectin-transfec ted cell line (300.19-L) during trauma-induced inflammation in rat mes enteric venules. HL-60 cells, which express no L-selectin but abundant sLe(x), rolled effectively immediately after abdominal surgery. HL-60 cell rolling was almost completely abolished by pretreatment with sia lidase or monoclonal antibody (MoAb) AM-3 recognizing sLe(x), and was reduced by about 80% by O-sialoglycoprotein-endopeptidase (OSGP). By c ontrast, 300.19-L cells rolled poorly immediately after surgery but ro lled well between 40 and 120 minutes after surgery. Their rolling was completely inhibited by the blocking L-selectin MoAb LAM1-3, but not b y a binding control MoAb. PMN express both L-selectin and clustered, s ialylated glycoproteins including P-selectin glycoprotein ligand-1 (PS GL-1). PMN showed effective rolling at all times, which was abolished by sialidase or MoAb AM-3 pretreatment during the first 30 minutes aft er surgery, but not later, when PMN rolling was largely L-selectin-dep endent. We conclude that in trauma-induced inflammation, a two-step me chanism accounts for most of myeloid cell rolling, which initially req uires O-glycans and subsequently depends on L-selectin function. (C) 1 995 by The American Society of Hematology.