Summary Thymic stromal lymphopoetin (TSLP) influences numerous immune functions, including those in the colonic mucosa. Here we report that TSLP-deficient (Tslp-/-) mice, did not exhibit increased inflammation during dextran sodium sulfate (DSS)-induced colitis, but failed to recover from disease, resulting in death. Increased localized neutrophil elastase (NE) activity during overt inflammation was observed in Tslp-/- mice, and was paralleled by reduced expression of an endogenous inhibitor, secretory leukocyte peptidase inhibitor (SLPI). Pharmacological inhibition of NE, or treatment with rSLPI reduced DSS-induced mortality in Tslp-/- mice. Signaling through TSLPR on non-hematopoietic cells was sufficient for recovery from DSS-induced colitis. Expression of the receptor occurred on intestinal epithelial cells (IEC), with stimulation inducing SLPI expression. Therefore, TSLP is critical in mediating mucosal healing following insult, and functions in a non-redundant capacity that is independent of restraining T helper 1 (Th1) and Th17 cell cytokine production.

CD83 is the major surface marker identifying mature dendritic cells (DCs). In this study, we report the generation of reporter mice expressing EGFP under the control of the CD83 promoter. We have used these mice to characterize CD83 expression by various immune system cell types both in vivo and ex vivo and under steady-state conditions and in response to stimulation with a Toll-like receptor (TLR) ligand. With those mice we could prove in vivo that the CD83 promoter is highly active in all DCs and B cells in lymphoid organs. Interestingly, this promoter activity in B cells mainly depended on the stage of development, is up-regulated in the late pre-B cell stage, and was maintained on a high level in all peripheral B cells. We also confirmed that CD83 in those cells is mainly intracellular but is up-regulated after TLR stimulation. Otherwise, CD83 promoter activity in T cells seemed to depend on stimulation and could be found mainly in CD4 ؉ CD25 ؉ and CD8 ؉ CD25 ؉ T cells and in CD4 ؉ and CD8 ؉ memory cells. In addition, we identified the murine homologues of the human CD83 splice variants. In contrast to those in human, those extremely rare short transcripts were never found without the expression of the highly dominant full-length form. So, the murine CD83 surface expression is mainly regulated posttranslationally in vivo. Our CD83 reporter mice represent a useful mouse model for monitoring the activation status and migration of DCs and lymphocytes under various conditions, and our results provide much needed clarification of the true nature of CD83 promoter activity.immune system ͉ mouse model ͉ intravital microscopy T he primary cells mediating adaptive responses are T and B lymphocytes and dendritic cells (DCs). A DC's ontogeny, state of differentiation, and degree of maturation governs its expression of a plethora of membrane-bound and soluble molecules that can induce immunostimulatory and immunosuppressive responses (1-3). Maturing DCs up-regulate certain cell surface molecules that greatly enhance their ability to present antigen and activate naive CD4 ϩ and CD8 ϩ T cells. Among these molecules is CD83, first described by Zhou et al. (4), CD83 is one of the most useful markers for identifying mature DCs capable of activating naïve T cells (5-8). CD83 expression also occurs on certain T cell subsets (9, 10), B cells (10-12), and murine thymic epithelial cells (13,14). Studies of CD83 transcription have shown that it is mediated by NF-B during the induction of adaptive responses (15,16).CD83 is conserved from fish species to mammals (17), with mouse CD83 sharing 63% amino acid identity with human CD83 (18,19). To date, two protein isoforms of CD83 have been reported in humans: a membrane-bound form (mCD83) (5) and a soluble form (sCD83) (20). mCD83 is a highly glycosylated surface protein of the Ig superfamily with a molecular mass of 40-45 kDa (5, 21). mCD83 contains an extracellular Ig-like V domain at the N terminus, a short intracellular cytoplasmic domain of 39 aa, and one transmembrane domain (5). ...