The Dichotomous Pattern of IL-12R and IL-23R Expression Elucidates the Role of IL-12 and IL-23 in Inflammation

IL-12 and IL-23 cytokines respectively drive Th1 and Th17 type responses. Yet, little is known regarding the biology of these receptors. As the IL-12 and IL-23 receptors share a common subunit, it has been assumed that these receptors are co-expressed. Surprisingly, we find that the expression of each of these receptors is restricted to specific cell types, in both mouse and human. Indeed, although IL-12Rβ2 is expressed by NK cells and a subset of γδ T cells, the expression of IL-23R is restricted to specific T cell subsets, a small number of B cells and innate lymphoid cells. By exploiting an IL-12- and IL-23-dependent mouse model of innate inflammation, we demonstrate an intricate interplay between IL-12Rβ2 NK cells and IL-23R innate lymphoid cells with respectively dominant roles in the regulation of systemic versus local inflammatory responses. Together, these findings support an unforeseen lineage-specific dichotomy in the in vivo role of both the IL-12 and IL-23 pathways in pathological inflammatory states, which may allow more accurate dissection of the roles of these receptors in chronic inflammatory diseases in humans

Th17 cytokines and arthritis

Th17 cells are implicated in human autoimmune diseases, such as rheumatoid arthritis (RA), although it has not been established whether this persistent destructive arthritis is driven by Th1 and/or Th17 cells. Interleukin-17A (IL-17A) contributes to the pathogenesis of arthritis as has been shown in several experimental arthritis models. Importantly, recent data from first clinical trials with anti-IL-17A antibody treatment in psoriatic arthritis patients and RA patients looks promising. This review summarizes the findings about the role of Th17 cells in arthritis and discusses the impact of the different Th17 cytokines in the pathogenesis of this disease. However, further studies are needed to unravel the interplay between IL-17A and other Th17 cytokines such as IL-17F, IL-22, and IL-21 in the pathoimmunological process of this crippling disease, in particular, whether regulating Th17 cell activity or specific combinations of Th17 cytokines will have additional value compared to neutralizing IL-17A activity alone. Moreover, tumor necrosis factor-positive Th17 cells are discussed as potential dangerous cells in driving persistent arthritis in human early RA

Are we ready to start studies of Th17 cell manipulation as a therapy for cancer?

From a therapeutic perspective, the bourgeoning literature on Th17 cells should allow us to decide whether to rationally pursue the manipulation of Th17 cells in cancer. The purpose of this review is to attempt a synthesis of a number of contradictory conclusions as to the role that these cells are playing in the process of tumourigenesis in order to provide guidance as to whether our current understanding is sufficient to safely pursue Th17-targeted therapy in cancer at this time. Th17 cells are a highly plastic population and the cytokine drivers for Th17 cell generation and skewing will vary between various cancers and importantly between different sites of tumour involvement in any individual patient. The net impact of the pro-angiogenic IL-17 produced not only by Th17 cells but by other cells particularly macrophages and the anti-tumour effects of Th1/Th17 cells will in turn be determined by the complex interplay of diverse chemokines and cytokines in any tumour microenvironment. Th17 cells that fail to home to tumours may be immunosuppressive. The complexity of IL-17 and Th17 dynamics makes easy prediction of the effects of either enhancing or suppressing Th17 cell differentiation in cancer problematic