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Background: Atopic dermatitis skin lesions demonstrate increased expression of IL-25 by keratinocytes and increased numbers of type 2 innate lymphoid cells (ILC2s) that express high levels of IL-25 receptor (IL-25R). IL-13 is expressed in atopic dermatitis skin lesions and plays an important role in pathogenesis of the disease., Objective: Our aim was to determine the role of IL-25 and ILC2s in a mouse model of antigen-driven allergic skin inflammation., Methods: Wild-type mice; mice that express an Il13-driven enhanced green fluorescent protein; and mice that lack IL-25R, IL-25 in keratinocytes, or IL-13 or IL-25R in ILC2s were subjected to acute or chronic epicutaneous sensitization with ovalbumin. Sensitized skin was examined by histology for epidermal thickening. Cellular infiltrates were analyzed for surface markers and intracellular expression of enhanced green fluorescent protein by flow cytometry. Gene expression was quantitated by RT quantitative PCR., Result: In both acute and chronic antigen-driven allergic skin inflammation, signaling by keratinocyte-derived IL-25 in ILC2s is important for epidermal hyperplasia, dermal infiltration by CD4 + T cells, and cutaneous expression of Il13 and the IL-13-dependent T H 2-cell-attracting chemokines Cc17 and Ccl22. ILCs are the major source of IL-13 in acutely sensitized mouse skin, whereas T cells are its major source in chronically sensitized mouse skin., Conclusion: ILC2 activation by IL-25 is essential for IL-13 expression at sites of allergic skin inflammation., (Copyright © 2020 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: Psoriasis is a systemic inflammatory disease in which IL-17 and IL-22 levels are markedly increased in the skin and blood. The prevalent concept, using skin cells that are isolated from psoriatic plaques and examined after cell expansion and in vitro stimulation, is that IL-17 and IL-22 production essentially results from T cells and the rare type 3 innate lymphoid cells., Objective: We sought to examine the cellular source of IL-17A and IL-22 at the protein and transcriptional single-cell level immediately after ex vivo skin cell isolation from psoriatic plaques., Methods: Skin biopsy specimens were collected from patients with psoriasis, as well as from patients with atopic dermatitis. Cell suspensions were prepared by combining mild enzymatic digestion and mechanical dissociation and analyzed for cytokine expression without prior in vitro culture and stimulation. Expression of IL-17 and IL-22 was quantified at the protein and mRNA single-cell level by using flow cytometry., Results: IL-22 is predominantly expressed by CD3(-)c-Kit(+) cells relative to CD3(+) T cells in lesional skin of patients with psoriasis and patients with atopic dermatitis. Strikingly, we identified c-Kit(+)FcεRI(+) mast cells as major IL-22 producers. The proportion of mast cells that produce IL-22 ranges from 20% to 80% in patients with psoriasis or those with atopic dermatitis. Skin mast cells express IL-22 and IL-17 mRNA. Conversely, IL-17-producing T cells outnumber IL-17-producing mast cells, which also express IL-17 receptor., Conclusion: Human skin mast cells are previously unrecognized IL-22 producers. We further established that skin mast cells express IL-17. Thus mast cells might play an important role in the physiopathology of chronic inflammatory skin disorders., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: Dendritic cells (DCs) are crucial to shape the adaptive immune response. Extensive in vitro manipulation reprograms T(H)2 and T(H)17 cell lines into T(H)1 cells, leading to the concept of CD4(+) T(H) cell subset plasticity. The conversion of memory T(H)17 cells into T(H)2 cells or vice versa remains to be clarified., Objective: We examined the localization of T(H)17/T(H)2 cells in vivo, their cellular origin (T(H)2 vs T(H)17), and the underlying mechanisms that drive the generation of these double T(H) producers., Methods: Antigen-loaded bone marrow-derived DCs (ovalbumin-DCs) were repeatedly administered locally (intratracheally) or systemically (intravenously) to naive mice to elicit chronic airway inflammation. Inflamed lungs and mediastinal lymph nodes were examined for the presence of IL-17(+)IL-13(+)IL-4(+)CD4(+) T cells that coexpressed retinoic acid receptor-related orphan receptor γt and GATA-3 (T(H)17/T(H)2)., Results: We show that repetitive administration of inflammatory ovalbumin-DCs, locally or systemically, promoted the development of antigen-specific T(H)17/T(H)2 cells in lungs and mediastinal lymph nodes. Immunized mice had IgE-independent and steroid-resistant airway inflammation with a mixed neutrophil and eosinophil infiltration of the bronchoalveolar lavage fluid. Airway inflammatory signal regulatory protein α-positive DCs reprogrammed in vitro-generated T(H)17 but not T(H)2 cells, as well as lung effector T(H) cells, into T(H)17/T(H)2 cells., Conclusion: We demonstrate the existence of T(H)17/T(H)2 cells that express GATA-3 in inflamed tissues and their T(H)17 origin. We further propose that repeated immunization with inflammatory DCs prevails on the route of DC administration to drive T(H)17/T(H)2-associated chronic lung inflammation., (Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Dendritic cells (DCs) are essential for the initiation and maintenance of T(H)2 responses to inhaled antigen that lead to the establishment of allergic diseases. Two subpopulations of nonplasmacytoid DCs (ie, CD11b(low)CD103+ and CD11b(high)CD103(-)) are found in lung/airway tissues. Yet the identification and migratory properties of the DC subset that contributes to T(H)2-mediated responses remain to be clarified. CD47, a signal regulatory protein (SIRP)-alpha partner, reportedly governed skin DC migration., Objective: We here thought to investigate the role of CD47/SIRP-alpha interactions in airway DC trafficking and the development of allergic airway inflammation., Methods: We characterized the DC influx into lungs and mediastinal lymph nodes in CD47(-/-) and CD47(+/+) BALB/c mice by using experimental models of allergic asthma. Mice were systemically (intraperitoneal ovalbumin/alum) or locally (intratracheal ovalbumin-loaded bone marrow-derived DCs) immunized and challenged by ovalbumin aerosol. We also evaluated the consequences of SIRP-alpha-Fc fusion molecule administration on the induction of airway disease in BALB/c mice., Results: SIRP-alpha selectively identified the CD11b(high)CD103(-) DC subset that predominantly accumulated in mediastinal lymph nodes during airway inflammation. However, CD103(-)SIRP-alpha+ DC trafficking, T(H)2 responses, and airway disease were impaired in CD47(-/-) mice. Importantly, the adoptive transfer of CD103(-) SIRP-alpha+CD47(+/+) but not CD47(-/-) DCs elicited a strong T(H)2 response in CD47(-/-) mice. Finally, the administration of SIRP-alpha-Fc molecule protected BALB/c mice from allergic airway inflammation., Conclusion: Lung CD11b(high)CD103(-)SIRP-alpha+ DC migration is governed by self-CD47 expression, and manipulation of the CD47/SIRP-alpha pathway suppresses CD103(-)SIRP-alpha(+) DC-driven pathogenic T(H)2 responses and airway inflammation.

Background: Analysis of naturally occurring T regulatory CD4+ (nTreg) cells in human diseases is hampered by the lack of specific surface marker. Indeed, the CD25 antigen, which is typically used to identify nTreg cells, is also expressed on activated effector T cells., Objective: We sought to examine whether CD4+ T cells bearing CD103 are suppressor cells, regardless of CD25 coexpression., Methods: We first compared freshly isolated tonsillar CD103+ CD25- cells with their CD103- CD25high counterparts for their capacity to suppress T-cell response and their expression of FoxP3 mRNA. Next CD103 was induced on neonatal or adult CD4+ T cells stimulated with allogeneic dendritic cells, and the CD103+ and CD103- fractions were compared as above., Results: Tonsillar CD4+ CD103+ CD25- T cells displayed comparable suppressive activity and contained similar amounts of FoxP3 mRNA as their CD103- CD25high counterparts. In vitro-generated alloantigen-primed CD103+ cells coexpressed CD25, suppressed T-cell activation, and contained more FoxP3 mRNA than the CD103- CD25+ cells isolated from the same cultures. Finally, neonatal alloreactive cells contained more CD103+ Treg cells than their adult counterparts and, unlike the latter, became hyporesponsive to the priming alloantigens., Conclusions: The examination of CD103 and CD25 coexpression allows identification of 3 subsets of human CD4+ nTreg cells, and the detection of CD103 on CD4+ T cells identifies nTreg cells, regardless of CD25 coexpression., Clinical Implications: The greater induction of CD103+ suppressor cells by cord blood should be related to its successful clinical use as an alternative to adult bone marrow transplantation.