Potent induction of α(1,3)-fucosyltransferase VII in activated CD4⁺ T cells by TGF-β1 through a p38 mitogen-activated protein kinase-dependent pathway

Homing of effector T cells to sites of inflammation, particularly in the skin, is dependent on T cell expression of ligands for the endothelial selectins. Underlying expression of these ligands is the expression of α(1,3)-fucosyltransferase VII (FucT-VII), a FucT essential for biosynthesis of selectin ligands. FucT-VII is sharply induced in activated T cells by IL-12, but cytokines other than IL-12 that induce FucT-VII and functional selectin ligands have not been identified, and are likely to be important in homing of T cells to other selectin-dependent sites. Screening of a number of cytokines known to be active on T cells identified only TGF-β1 as able to up-regulate FucT-VII mRNA levels and selectin ligands on activated CD4 T cells. The sharp increase in FucT-VII induced by TGF-β1 in activated T cells was completely blocked by pharmacologic inhibition of p38 mitogen-activated protein kinase, but was unaffected by mitogen-activated protein/extracellular signal-related kinase kinase inhibitors. The selective ability of TGF-β1 to induce selectin ligands on activated T cells is likely important for T cell homing to the gut, which is a strongly selectin-dependent site, and correlates with the ability of TGF-β1 to coordinately induce other gut-associated homing pathways.