Abstract
Selectins are glycan-binding adhesion molecules that mediate the initial steps of leukocyte recognition of endothelium. Cytokines control numerous aspects of CD4 Th cell differentiation, but how cytokines control the induction of ligands for E- and P-selectin on Th cell subsets remains poorly understood. Among 20 cytokines that affect Th cell differentiation, we identified six that induce expression of selectin ligands on murine CD4 T cells above the low levels associated with TCR engagement: IL-12, IL-18, IL-27, IL-9, IL-25, and TGF-β1. Collectively, these six cytokines could potentially account for selectin ligand expression on all of the currently defined nonsessile Th cell lineages, including Th1, Th2, Th9, and Th17 cells, as well as regulatory T cells. Induction of selectin ligand expression by each of these six cytokines was almost completely inhibited by pharmacologic inhibition of p38 MAPK, but not other MAPKs, or by conditional genetic deletion of p38α MAPK. Analysis of the expression of key glycosyltransferase genes revealed that p38α signaling was selectively required for induction of Fut7 and Gcnt1 but not for the induction of St3gal4 or St3gal6. Constitutively active MKK6, an immediate upstream activator of p38 MAPK, induced selectin ligand expression equivalent to that of cytokines, and this induction was completely dependent on the expression of p38α. Our results identify the repertoire of cytokines responsible for selectin ligand induction on CD4 T cells and provide a mechanistic link between Th cell development and T cell migration.