Discordant expression of selectin ligands and sialyl Lewis x-related epitopes on murine myeloid cells

Abstract

Murine leukocytes are thought to express α2-3-sialylated and α1-3-fucosylated selectin ligands such as sialyl Lewis x (sLex), although monoclonal antibodies (mAbs) to sLex or Lex reportedly do not bind to murine leukocytes. We observed that P-and E-selectin bound to pronase-sensitive ligands on murine monocytic WEHI-3 cells and murine neutrophils, indicating that the ligands for both selectins are glycoproteins. CSLEX-1, HECA-452, and other widely used mAbs to sLex and Lex did not bind to WEHI-3 cells and bound at very low levels to murine neutrophils. Only the anti-sLex mAbs 2H5 and KM93, which also recognize nonfucosylated glycans, bound to WEHI-3 cells. 2H5 and KM93 bound to pronase-resistant structures, indicating that the mAbs did not identify selectin ligands. Treatment of WEHI-3 cells with glycosidases or chlorate demonstrated that sialic acid modifications, α1-3-galactosylation, or sulfation did not mask epitopes for mAbs to sLex or Lex. Compared to human promyelocytic HL-60 cells, WEHI-3 cells and murine neutrophils expressed low α1-3-fucosyltransferase activities. Consistent with very low endogenous fucosylation, forced fucosylation of intact WEHI-3 cells or murine neutrophils by exogenous α1-3-fucosyltransferase FTVI and GDP-fucose created many new epitopes for anti-sLex mAbs such as HECA-452 and CSLEX-1. Nevertheless, forced fucosylation of intact cells did not significantly augment their ability to bind to fluid-phase P- or E-selectin or to roll on immobilized P- or E-selectin under flow. These data suggest that murine myeloid leukocytes fucosylate only a few specific glycans, which interact preferentially with P- and E-selectin. © 2002 by The American Society of Hematology.