Fungal diseases represent an important paradigm in immunology, as they can result from either a lack of recognition by the immune system or overactivation of the inflammatory response. Research in this field is entering an exciting period of transition from studying the molecular and cellular bases of fungal virulence to determining the cellular and molecular mechanisms that maintain immune homeostasis with fungi. The fine line between these two research areas is central to our understanding of tissue homeostasis and its possible breakdown in fungal infections and diseases. Recent insights into immune responses to fungi suggest that functionally distinct mechanisms have evolved to achieve optimal host-fungus interactions in mammals.

Immunity to fungal infections

The IL-10 family of cytokines consists of nine members: IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, and the more distantly related IL-28A, IL-28B, and IL-29. Evolutionarily, IL-10 family cytokines emerged before the adaptive immune response. These cytokines elicit diverse host defense mechanisms, especially from epithelial cells, during various infections. IL-10 family cytokines are essential for maintaining the integrity and homeostasis of tissue epithelial layers. Members of this family can promote innate immune responses from tissue epithelia to limit the damage caused by viral and bacterial infections. These cytokines can also facilitate the tissue-healing process in injuries caused by infection or inflammation. Finally, IL-10 itself can repress proinflammatory responses and limit unnecessary tissue disruptions caused by inflammation. Thus, IL-10 family cytokines have indispensable functions in many infectious and inflammatory diseases.

Regulation and Functions of the IL-10 Family of Cytokines in Inflammation and Disease

https://www.rs.tus.ac.jp/iwakuralab/pdf/review_il17family.pdf

Functional Specialization of Interleukin-17 Family Members

Background In this phase 2, randomized, double-blind, placebo-controlled, dose-ranging study, we assessed the efficacy and safety of brodalumab (AMG 827), a human anti–interleukin-17–receptor monoclonal antibody, for the treatment of moderate-to-severe plaque psoriasis. Methods We randomly assigned patients with a score of 12 or higher on the psoriasis area-and-severity index (PASI, on which scores range from 0 to 72, with higher scores indicating more severe disease) and with 10% or more of their body-surface area affected by psoriasis to receive brodalumab (70 mg, 140 mg, or 210 mg at day 1 and weeks 1, 2, 4, 6, 8, and 10 or 280 mg monthly) or placebo. The primary end point was the percentage improvement from baseline in the PASI score at week 12. Secondary end points included improvement of at least 75% and at least 90% in the PASI score and the score on the static physician's global assessment at week 12. Results A total of 198 patients underwent randomization. At week 12, the mean percentage improvem...

https://www.nejm.org/doi/pdf/10.1056/NEJMoa1109017

Brodalumab, an Anti–Interleukin-17–Receptor Antibody for Psoriasis

Chronic mucocutaneous candidiasis disease (CMCD) is characterized by recurrent or persistent infections of the skin, nails, and oral and genital mucosae caused by Candida albicans and, to a lesser extent, Staphylococcus aureus , in patients with no other infectious or autoimmune manifestations. We report two genetic etiologies of CMCD: autosomal recessive deficiency in the cytokine receptor, interleukin-17 receptor A (IL-17RA), and autosomal dominant deficiency of the cytokine interleukin-17F (IL-17F). IL-17RA deficiency is complete, abolishing cellular responses to IL-17A and IL-17F homo- and heterodimers. By contrast, IL-17F deficiency is partial, with mutant IL-17F–containing homo- and heterodimers displaying impaired, but not abolished, activity. These experiments of nature indicate that human IL-17A and IL-17F are essential for mucocutaneous immunity against C. albicans , but otherwise largely redundant.

https://science.sciencemag.org/content/sci/332/6025/65.full.pdf

Chronic Mucocutaneous Candidiasis in Humans with Inborn Errors of Interleukin-17 Immunity

https://www.jidonline.org/article/S0022-202X(15)34836-3/pdf

Circulating Th17, Th22, and Th1 cells are increased in psoriasis.

IL-23 and Th17 cells producing IL-17A and IL-22 are found in excess in skin affected by psoriasis. Previous studies showed that IL-22, but not IL-17A, mediates psoriasis-like epidermal hyperplasia following recombinant murine (rm)IL-23 injections into skin. To further investigate the role of IL-17A, ears of mice were injected with rmIL-23. Investigators blinded to treatment conditions and mouse genotypes measured ear swelling, epidermal thickness, and cytokine expression. In wild-type (WT) mice, rmIL-23 induced ear swelling (p < 0.001, all p values versus saline), epidermal hyperplasia by histology (p < 0.001) and confocal microscopy (p < 0.004), and expression of both IL-17A and IL-22. As expected, rmIL-23 injections into IL-22(-/-) mice resulted in relatively little ear swelling (p < 0.09) and epidermal hyperplasia (p < 0.51 by histology and p < 0.75 by confocal microscopy). Notably, rmIL-23 injections into IL-17A(-/-) mice produced little ear swelling (p < 0.001, versus IL-23-injected WT mice) and epidermal hyperplasia (p < 0.001 by histology and p < 0.005 by confocal microscopy), even though IL-22 was readily induced in these mice. Furthermore, systemic delivery of blocking Abs directed against either IL-22 or IL-17A completely inhibited IL-23-induced epidermal hyperplasia in WT mice. These results demonstrate that IL-17A, like IL-22, is a downstream mediator for IL-23-induced changes in murine skin and that both of these Th17 cytokines are necessary to produce IL-23-mediated skin pathology. IL-17A may represent an attractive therapeutic target in individuals with psoriasis by blocking downstream effects of IL-23.

/pdf/il-23-mediated-psoriasis-like-epidermal-hyperplasia-is-1dsuqak30f.pdf

IL-23–Mediated Psoriasis-Like Epidermal Hyperplasia Is Dependent on IL-17A

IL-23 and Th17 cells play important roles in host defense against systemic infections with extracellular bacteria and fungi, although their roles in immunity against localized skin infections are less well defined. Here, the contributions of IL-23 and Th17 cytokines in host defense against cutaneous Candida albicans infection were evaluated. Mice deficient in IL-23 or IL-17A demonstrated delayed healing and decreased IL-17A production after skin infection with C. albicans compared with wild-type mice or mice deficient in IL-12 or IL-22. Histologic examination revealed epidermal hyperplasia overlying infected dermis four days postinoculation in wild-type mice. In IL-23–deficient mice, fungal burden was greater in skin, neither IL-17A nor IL-22 mRNAs were expressed postinfection, and these mice demonstrated only minimal epidermal hyperplasia. Exogenous recombinant IL-17A injected at the site of skin infection promoted more rapid healing of candidiasis in both wild-type mice and mice deficient in IL-23 and IL-12. Taken together, these results demonstrate that IL-23 and IL-17A, but not IL-12 and IL-22, are required for optimal host defense against cutaneous candidiasis. In addition, recombinant IL-17A may serve as a potential therapy to enhance healing in individuals with chronic cutaneous candidiasis.

/pdf/il-23-and-il-17a-but-not-il-12-and-il-22-are-required-for-1lm86tvz3h.pdf

IL-23 and IL-17A, but Not IL-12 and IL-22, Are Required for Optimal Skin Host Defense against Candida albicans

DataSupplementary01001.DC1.html http://www.jimmunol.org/content/suppl/2010/12/22/jimmunol.10Subscriptionsonline at http://www.jimmunol.org/subscriptionsInformation about subscribing to The Journal of Immunology isPermissionshttp://www.aai.org/ji/copyright.html Submit copyright permission requests atEmail Alertsat http://www.jimmunol.org/etoc/subscriptions.shtml/ Receive free email-alerts when new articles cite this article. Sign up

Shinji Kagami

Papers

Circulating Th17, Th22, and Th1 cells are increased in psoriasis.

IL-23–Mediated Psoriasis-Like Epidermal Hyperplasia Is Dependent on IL-17A

IL-23 and IL-17A, but Not IL-12 and IL-22, Are Required for Optimal Skin Host Defense against Candida albicans

Hyperplasia Is Dependent on IL-17A Mediated Psoriasis-Like Epidermal - IL-23