Cytokines of the interleukin-1 (IL-1) family, such as IL-1 alpha/beta and IL-18, have important functions in host defense, immune regulation, and inflammation. Insight into their biological functions has led to novel therapeutic approaches to treat human inflammatory diseases. Within the IL-1 family, IL-1 alpha/beta, IL-1Ra, and IL-18 have been matched to their respective receptor complexes and have been shown to have distinct biological functions. The most prominent orphan IL-1 receptor is ST 2. This receptor has been described as a negative regulator of Toll-like receptor-IL-1 receptor signaling, but it also functions as an important effector molecule of T helper type 2 responses. We report a member of the IL-1 family, IL-33, which mediates its biological effects via IL-1 receptor ST 2, activates NF-kappaB and MAP kinases, and drives production of T(H)2-associated cytokines from in vitro polarized T(H)2 cells. In vivo, IL-33 induces the expression of IL-4, IL-5, and IL-13 and leads to severe pathological changes in mucosal organs.

Autoimmunity plays a key role in the immunopathogenesis of psoriasis; however, little is known about the recruitment of pathogenic cells to skin lesions. We report here that the CC chemokine, macrophage inflammatory protein-3α, recently renamed CCL20, and its receptor CCR6 are markedly up-regulated in psoriasis. CCL20-expressing keratinocytes colocalize with skin-infiltrating T cells in lesional psoriatic skin. PBMCs derived from psoriatic patients show significantly increased CCR6 mRNA levels. Moreover, skin-homing CLA+ memory T cells express high levels of surface CCR6. Furthermore, the expression of CCR6 mRNA is 100- to 1000-fold higher on sorted CLA+ memory T cells than other chemokine receptors, including CXCR1, CXCR2, CXCR3, CCR2, CCR3, and CCR5. In vitro, CCL20 attracted skin-homing CLA+ T cells of both normal and psoriatic donors; however, psoriatic lymphocytes responded to lower concentrations of chemokine and showed higher chemotactic responses. Using ELISA as well as real-time quantitative PCR, we show that cultured primary keratinocytes, dermal fibroblasts, and dermal microvascular endothelial and dendritic cells are major sources of CCL20, and that the expression of this chemokine can be induced by proinflammatory mediators such as TNF-α/IL-1β, CD40 ligand, IFN-γ, or IL-17. Taken together, these findings strongly suggest that CCL20/CCR6 may play a role in the recruitment of T cells to lesional psoriatic skin.

In contrast to naive lymphocytes, memory͞effector lymphocytes can access nonlymphoid effector sites and display restricted, often tissue-selective, migration behavior. The cutaneous lymphocyteassociated antigen (CLA) defines a subset of circulating memory T cells that selectively localize in cutaneous sites mediated in part by the interaction of CLA with its vascular ligand E-selectin. Here, we report the identification and characterization of a CC chemokine, cutaneous T cell-attracting chemokine (CTACK). Both human and mouse CTACK are detected only in skin by Southern and Northern blot analyses. Specifically, CTACK message is found in the mouse epidermis and in human keratinocytes, and anti-CTACK mAbs predominantly stain the epithelium. Finally, CTACK selectively attracts CLA ؉ memory T cells. Taken together, these results suggest an important role for CTACK in recruitment of CLA ؉ T cells to cutaneous sites. CTACK is predominantly expressed in the skin and selectively attracts a tissue-specific subpopulation of memory lymphocytes.

IL-33 (IL-1F11) is a recently described member of the IL-1 family of cytokines that stimulates the generation of cells, cytokines, and Igs characteristic of a type 2 immune response. IL-33 mediates signal transduction through ST2, a receptor expressed on Th2 and mast cells. In this study, we demonstrate that IL-33 and ST2 form a complex with IL-1R accessory protein (IL-1RAcP), a signaling receptor subunit that is also a member of the IL-1R complex. Additionally, IL-1RAcP is required for IL-33-induced in vivo effects, and IL-33-mediated signal transduction can be inhibited by dominant-negative IL-1RAcP. The implications of this shared usage of IL-1RAcP by IL-1(α and β) and IL-33 are discussed.

We report the identification and characterization of a novel CC chemokine designated CCL28 and its receptor CCR10, known previously as orphan G-protein-coupled receptor GPR2. Human and mouse CCL28 share 83% identity at the amino acid and 76% at the nucleic acid levels. We also identified the mouse homologues of CCL28 and of CCR10, which map to mouse chromosomes 13 and 11, respectively. CCL28 is expressed in a variety of human and mouse tissues, and it appears to be predominantly produced by epithelial cells. Both human and mouse CCL28 induce calcium mobilization in human and mouse CCR10-expressing transfectants. CCL28 desensitized the calcium mobilization induced in CCR10 transfectants by CCL27, indicating that these chemokines share this new chemokine receptor. In vitro, recombinant human CCL28 displays chemotactic activity for resting CD4 or CD8 T cells.