α(1,3)-Fucosyltransferase VII and α(2,3)-Sialyltransferase IV Are Up-Regulated in Activated CD4 T Cells and Maintained After Their Differentiation into Th1 and Migration into Inflammatory Sites

Activated Th1 CD4 T cells bind to P-selectin and migrate into inflamed tissue, whereas Th2 cells do not. We show that α(1,3)-fucosyltransferase VII (FucT-VII) and α(2,3)-sialyltransferase IV (ST3GalIV), which are crucial for the biosynthesis of functional P-selectin ligands, are absent in naive CD4 T cells, but are rapidly up-regulated upon activation. Th1 or Th2 differentiation in the presence of polarizing cytokines leads to down-regulation of FucT-VII mRNA selectively in Th2 but not in Th1 cells. Influencing the differentiation by varying the priming dose of antigenic peptide results in similar FucT-VII down-regulation only in Ag-specific Th2 cells. ST3GalIV levels remain elevated. FucT-VII and ST3GalIV mRNAs are also up-regulated by Th1 cells primed in vivo and recruited into the lymph nodes draining delayed-type hypersensitivity sites. We identify FucT-VII gene expression as a principal difference between Th1 and Th2 cells, and underscore the importance of FucT-VII and ST3GalIV expression for the biosynthesis of functional selectin ligands.

α(1,3)-Fucosyltransferase VII-Dependent Synthesis of P- and E-Selectin Ligands on Cultured T Lymphoblasts

T lymphocytes up-regulate the synthesis of ligands for E- and P-selectin during proliferative responses in vivo and in vitro. Previous studies from our laboratories indicated that the α(1,3)-fucosyltransferase FucT-VII regulates the synthesis of E-selectin ligands and sialylated Lewisx-related epitopes (sLex-related epitopes) in human T lymphoblasts. The current report shows that production of both P- and E-selectin ligands is FucT-VII dependent, but peak synthesis of each occurs at different levels of fucosyltransferase activity in intact cells. In brief, FucT-VII mRNA levels were higher in cultured T lymphoblasts expressing sLex-related epitopes and both selectin ligands than in cells expressing P-selectin ligands alone. However, synthesis of the epitopes and both selectin ligands required the FucT-VII enzyme in transfected Molt-4 cells. In contrast, neither constitutive nor transfection-enhanced levels of the FucT-IV enzyme generated active P-selectin ligands in these lines. In addition, targeted deletion of the FucT-VII gene in mice markedly inhibited the synthesis of both P- and E-selectin ligands during blast transformation in vitro. Finally, the optimal synthesis of active P-selectin ligands occurred at lower level of FucT-VII activity than required for synthesis of equally active E-selectin ligands in both cultured T lymphoblasts and FucT-VII transfectants. Consequently, the FucT-VII enzyme is essential for the synthesis of both P- and E-selectin ligands by T lymphoblasts, and its activity determines whether P-selectin ligands are expressed alone or in conjunction with E-selectin ligands and sLex-related epitopes on human T cells.

An sLex-Deficient Variant of HL60 Cells Exhibits High Levels of Adhesion to Vascular Selectins: Further Evidence That HECA-452 and CSLEX1 Monoclonal Antibody Epitopes Are Not Essential for High Avidity Binding to Vascular Selectins

Selectins are carbohydrate-binding cell adhesion molecules that play a key role in the initiation of inflammatory responses. Several studies have suggested that the sialylated, fucosylated tetrasaccharide sialyl Lewis X (sLex) is an important component of leukocyte ligands for E- and P-selectin. We have identified a stable variant of the HL60 cell line, HL60var, which displays a nearly complete absence of staining with several mAb directed against sLex and/or sLex-related structures. HL60var also exhibits a concomitant increase in reactivity with mAb directed against the unsialylated Lewis X (Lex/CD15) structure. Despite this sLex deficiency, HL60var binds well to both E- and P-selectin. No significant differences in expression of α1,3-fucosyltransferases, C2GnT (Core2 transferase), or P-selectin glycoprotein ligand-1 between HL60var and typical sLexhigh HL60 cells were detected. Although the precise molecular basis for the sLex−/low phenotype of HL60var remains uncertain, flow cytometric analysis with the sialic acid-specific Limax flavus lectin revealed a sharp reduction in HL60var surface sialylation. Thus, the loss in mAb reactivity may result from a loss of sialic acid residues from the mAb carbohydrate epitope. However, binding of HL60var to E- and P-selectin remains sensitive to neuraminidase treatment. Taken together, these data indicate that high levels of surface sLex and/or related epitopes are not essential for interactions with vascular selectins, implying that as yet unidentified sialylated, fucosylated structures serve as physiologically relevant ligands for E- and P-selectin.