The Lymphoid Chemokine CCL21 Enhances the Migration- and CTL-Inducing Functions of Dendritic Cells

Abstract 1127

The migration of dendritic cells (DCs) to secondary lymphoid organs is very important to elicit an adaptive immune response in cancer immunotherapy. Here, we show the effect of lymphoid cytokine on the ability of maturing DCs to migrate in response to the lymph node-associated chemokines. The secondary-lymphoid organ chemokine (SLC/CCL21) during DC maturation dramatically enhanced DC migratory capacity responding to CCL21 and CCL19, and, moreover, produced strongly enhanced cytotoxic T cells, although it did not affect the expression of cell surface markers such as CD80, CD83, CD86, and CCR7 and the production of cytokines such as IL-12p70, IL-10, and IL-23. Mature DCs (mDCs) exposed by chemokine produced higher levels of CXCL10 (IP-10) that is one of the chemokines involved in Th1 attraction, but did not affect the production of Th2-attracting cytokine CCL22, compared with unstimulated mDCs. CCL21-exposed DCs induced strongly enhanced numbers of the interferon-g (IFN-g)-expressing antigen-specific CD8+ T cells against tumor-specific antigens in an CXCL10-dependent manner. Cytotoxic CD8+ T cells stimulated with CCL21-exposed DCs expressed higher level of IFN-g than those stimulated with control mDCs. Interestingly, generation of cytotoxic T cells (CTLs) stimulated by TNFa/IL-1b/IL-6/PGE₂-treated DCs (sDCs) supplemented with IP-10 produced strong cytotoxic T cells expressing higher level of IFN-g. Tetramer assay showed that CCL21-treated DCs enhanced generation of antigen-specific CTLs. Taken together, our data suggest that mDCs pre-stimulated by chemokine CCL21 enhanced migratory capacity to secondary lymphoid organs and produced strong cytotoxic T cells via IP-10 signaling pathway.