Interleukin-12 (IL-12) is a heterodimeric molecule composed of p35 and p40 subunits. Analyses in vitro have defined IL-12 as an important factor for the differentiation of naive T cells into T-helper type 1 CD4+ lymphocytes secreting interferon-gamma (refs 1, 2). Similarly, numerous studies have concluded that IL-12 is essential for T-cell-dependent immune and inflammatory responses in vivo, primarily through the use of IL-12 p40 gene-targeted mice and neutralizing antibodies against p40. The cytokine IL-23, which comprises the p40 subunit of IL-12 but a different p19 subunit, is produced predominantly by macrophages and dendritic cells, and shows activity on memory T cells. Evidence from studies of IL-23 receptor expression and IL-23 overexpression in transgenic mice suggest, however, that IL-23 may also affect macrophage function directly. Here we show, by using gene-targeted mice lacking only IL-23 and cytokine replacement studies, that the perceived central role for IL-12 in autoimmune inflammation, specifically in the brain, has been misinterpreted and that IL-23, and not IL-12, is the critical factor in this response. In addition, we show that IL-23, unlike IL-12, acts more broadly as an end-stage effector cytokine through direct actions on macrophages.

An efficient Th1-driven adaptive immune response requires activation of the T cell receptor and secretion of the T cell stimulatory cytokine IL-12 by activated antigen-presenting cells. IL-12 triggers Th1 polarization of naive CD4(+) T cells and secretion of IFN-gamma. We describe a new heterodimeric cytokine termed IL-27 that consists of EBI3, an IL-12p40-related protein, and p28, a newly discovered IL-12p35-related polypeptide. IL-27 is an early product of activated antigen-presenting cells and drives rapid clonal expansion of naive but not memory CD4(+) T cells. It also strongly synergizes with IL-12 to trigger IFN-gamma production of naive CD4(+) T cells. IL-27 mediates its biologic effects through the orphan cytokine receptor WSX-1/TCCR.

IL-23 is a heterodimeric cytokine composed of the IL-12p40 “soluble receptor” subunit and a novel cytokine-like subunit related to IL-12p35, termed p19. Human and mouse IL-23 exhibit some activities similar to IL-12, but differ in their capacities to stimulate particular populations of memory T cells. Like IL-12, IL-23 binds to the IL-12R subunit IL-12Rβ1. However, it does not use IL-12Rβ2. In this study, we identify a novel member of the hemopoietin receptor family as a subunit of the receptor for IL-23, “IL-23R.” IL-23R pairs with IL-12Rβ1 to confer IL-23 responsiveness on cells expressing both subunits. Human IL-23, but not IL-12, exhibits detectable affinity for human IL-23R. Anti-IL-12Rβ1 and anti-IL-23R Abs block IL-23 responses of an NK cell line and Ba/F3 cells expressing the two receptor chains. IL-23 activates the same Jak-stat signaling molecules as IL-12: Jak2, Tyk2, and stat1, -3, -4, and -5, but stat4 activation is substantially weaker and different DNA-binding stat complexes form in response to IL-23 compared with IL-12. IL-23R associates constitutively with Jak2 and in a ligand-dependent manner with stat3. The ability of cells to respond to IL-23 or IL-12 correlates with expression of IL-23R or IL-12Rβ2, respectively. The human IL-23R gene is on human chromosome 1 within 150 kb of IL-12Rβ2.

The skin-associated chemokine CCL27 (also called CTACK, ALP and ESkine) and its receptor CCR10 (GPR-2) mediate chemotactic responses of skin-homing T cells in vitro. Here we report that most skin-infiltrating lymphocytes in patients suffering from psoriasis, atopic or allergic-contact dermatitis express CCR10. Epidermal basal keratinocytes produced CCL27 protein that bound to extracellular matrix, mediated adhesion and was displayed on the surface of dermal endothelial cells. Tumor necrosis factor-alpha and interleukin-1beta induced CCL27 production whereas the glucocorticosteroid clobetasol propionate suppressed it. Circulating skin-homing CLA+ T cells, dermal microvascular endothelial cells and fibroblasts expressed CCR10 on their cell surface. In vivo, intracutaneous CCL27 injection attracted lymphocytes and, conversely, neutralization of CCL27-CCR10 interactions impaired lymphocyte recruitment to the skin leading to the suppression of allergen-induced skin inflammation. Together, these findings indicate that CCL27-CCR10 interactions have a pivotal role in T cell-mediated skin inflammation.

Increasing the in vivo residence times of protein therapeutics could decrease their dosing frequencies. We show that genetic fusion of an unstructured recombinant polypeptide of 864 amino acids, called XTEN, to a peptide or protein provides an apparently generic approach to extend plasma half-life. Allometric scaling suggests that a fusion of XTEN to the exenatide peptide should increase exenatide half-life in humans from 2.4 h to a projected time of 139 h. We confirmed the biological activity of the exenatide-XTEN fusion in mice. As extended stability might exacerbate undesirable side effects in some cases, we show that truncating the XTEN sequence can regulate plasma half-life. XTEN lacks hydrophobic amino acid residues that often contribute to immunogenicity and complicate manufacture. Based on data on XTEN fusions to exenatide, glucagon, GFP and human growth hormone, we expect that XTEN will enable dosing of otherwise rapidly cleared protein drugs at up to monthly intervals in humans.