Pathways controlling expression of glycosyltransferases in Th1 cells. Naive T cells express little or no FucT-VII, C2GlcNAcT-I, or ST3Gal-VI. T-cell activation through the TCR leads to activation of H-Ras and induction of FucT-VII, as well as induction or maintenance of constitutive levels of ST3Gal-IV. Whether ST3Gal-IV expression requires H-Ras is unknown. In addition, T-cell activation is associated with induction of the IL12R, particularly the IL12Rβ2 chain, and the IL12R is essential for activation of Stat4, which plays a major role in induction of C2GlcNAcT-I and a minor role in induction of ST3Gal-VI. T-bet plays a role through induction/maintenance of the IL12Rβ2, allowing up-regulation of C2GlcNAcT-I by Stat4; through direct up-regulation of C2GlcNAcT-I and ST3Gal-VI; and through up-regulation of FucT-VII by an as yet undetermined mechanism. Bold lines represent strong, presumably or known to be direct, effects; thin lines represent weak effects.