T cell stimulator cells, an efficient and versatile cellular system to assess the role of costimulatory ligands in the activation of human T cells.

It is well established that full activation of T cells requires the interaction of the TCR complex with the peptide-MHC complex (Signal 1) and additional signals (Signal 2). These second signals are generated by the interaction of costimulatory ligands expressed on antigen presenting cells with activating receptors on T cells. In addition, T cell responses are negatively regulated by inhibitory costimulatory pathways. Since professional antigen presenting cells (APC) harbour a plethora of stimulating and inhibitory surface molecules, the contribution of individual costimulatory molecules is difficult to assess on these cells. We have developed a system of stimulator cells that can give signal 1 to human T cells via a membrane bound anti-CD3 antibody fragment. By expressing human costimulatory ligands on these cells, their role in T cell activation processes can readily be analyzed. We demonstrate that T cell stimulator cells are excellent tools to study various aspects of human T cell costimulation, including the effects of immunomodulatory drugs or how costimulatory signals contribute to the in vitro expansion of T cells. T cell stimulator cells are especially suited for the functional evaluation of ligands that are implicated in costimulatory processes. In this study we have evaluated the role of the CD2 family member CD150 (SLAM) and the TNF family member TL1A (TNFSF15) in the activation of human T cells. Whereas our results do not point to a significant role of CD150 in T cell activation we found TL1A to potently costimulate human T cells. Taken together our results demonstrate that T cell stimulator cells are excellent tools to study various aspects of costimulatory processes

Induction of Targeted Cell Migration by Cutaneous Administration of a DNA Vector Encoding a Biologically Active Chemokine CCL21

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