The reduced lymphatic endothelium-directed trafficking of Ndst1-deficient DCs is noted in both immature as well as mature DCs and is not caused by a reduction in expression of the chemokine receptor CCR7 or in the maturation markers CD86 and MHCII (Figure 2). On the contrary, these markers are significantly increased along with reduced ovalbumin uptake, consistent with a more mature phenotype. CCL21 is a major chemokine responsible for DC migration from peripheral tissues toward lymph nodes [37]. Cellbound CCL21, a chemokine that binds strongly to HS, facilitates adhesion and random migration of DCs. This is distinguished from CCL19, a chemokine that does not bind to HS, and causes migration directed toward the source of the soluble chemokine without a significant role in adhesion of DCs [38,39]. Interestingly, because Ndst1-deficient DCs showed reduced migration toward both CCL21 and CCL19 (Supplemental Figure S2), mechanistic importance may also lie in the ability of the glycan to mediate receptor (i.e., CCR7) activity. This implies a possible key role for the glycan chain as part of a proteoglycan co-receptor. This is also consistent with our discovery of syndecan-4 as a putative co-receptor. Regardless, with respect to HS-binding ligands such as CCL21 (or others in the lymphatic microenvironment), interactions of basic amino acid–rich domains of a given chemokine with the sulfated glycan may critically regulate cell surface availability, concentrations, and gradients of the chemokine.