Abstract
Skin inflammation can induce local expression of CCL21, which is subsequently drained to lymph nodes (LNs) influencing their cellular composition. To determine whether the same can be achieved by dermal administration of a plasmid DNA (pDNA) encoding CCL21, we generated a pDNA-based gene construct allowing high-level expression of CCL21. Expression and secretion of biologically active CCL21 were confirmed in vitro by immunohistochemistry, western blot analysis, ELISA, and transwell chemotactic assays. In vivo experiments showed cellular expression of transgenic CCL21 after particle-mediated gene gun delivery of pDNA into skin. CCL21 was expressed in the epidermis, consequently secreted into the upper dermis, and transported into the draining LNs, which resulted in increased CCL21 concentration, total cell number, and frequencies of CD11c(+) DCs and CD4(+)/CD62L(+) naïve, CD4(+)/CD62L(-), and CD8(+)/CD62L(-) effector memory T-cells (expressing CCL21 receptors CCR7 or CXCR3), as well as retention of adoptively transferred T-lymphocytes, in the draining LNs of plt/plt mice (lacking endogenous expression of CCL21). Our studies show that biologically active CCL21 can be overexpressed by genetic means in vitro and in vivo. This strategy allows reconstitution of a genetic defect and colocalization of different cell types in the secondary lymphoid organs, an important prerequisite for targeted cell migration.