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1.  Activin and TGF-β signalling pathways are activated after allergen challenge in mild asthma 
Both transforming growth factor (TGF)-β1 and activin-A have been implicated in airway remodelling in asthma but the modulation of their specific signalling pathways after disease activation remains undefined.
To define the expression kinetics of TGF-β1, activin-A ligands and follistatin (a natural activin inhibitor), their Type I and Type II receptors (ALK-1, ALK-5 and ALK-4 and TβRII and ActRIIA/RIIB) and activation of signalling (via pSmad2), in the asthmatic airway following allergen challenge.
Immunohistochemistry was performed on bronchial biopsies from 15 mild atopic asthmatics (median age 25 years, median FEV1% predicted 97%) at baseline and 24 hours after allergen inhalation. Functional effects of activin-A were evaluated using cultured normal human bronchial epithelial (NHBE) cells.
pSmad2+ epithelial cells increased at 24 hours (p=0.03) and pSmad2 was detected in submucosal cells. No modulation of activin-A, follistatin or TGF-β1 expression was demonstrated. Activin receptor+ cells increased after allergen challenge.: ALK-4 in epithelium (p=0.04) and submucosa (p=0.04), and ActRIIA in epithelium (p=0.01). The TGF-β receptor ALK-5 expression was minimal in the submucosa at baseline and after challenge and was down-regulated in the epithelium after challenge (p=0.02), whereas ALK-1 and TβRII expression in the submucosa increased after allergen challenge (p=0.03 and p=0.004 respectively). ALK-1 and ALK-4 expression by T cells was increased after allergen challenge. Activin-A induced NHBE cell proliferation, was produced by NHBE cells in response to TNF-α, and down-regulated TNF-α and IL-13-induced chemokine production by NHBE cells.
Both TGF-β and activin signalling pathways are activated upon allergen provocation in asthma. Activin-A may contribute to resolution of inflammation.
PMCID: PMC4579560  PMID: 19733294
Asthma; activin-A; TGF-β1
2.  Circulating Conventional and Plasmacytoid Dendritic Cell Subsets Display Distinct Kinetics during In Vivo Repeated Allergen Skin Challenges in Atopic Subjects 
BioMed Research International  2014;2014:231036.
Upon allergen challenge, DC subsets are recruited to target sites under the influence of chemotactic agents; however, details pertinent to their trafficking remain largely unknown. We investigated the kinetic profiles of blood and skin-infiltrating DC subsets in twelve atopic subjects receiving six weekly intradermal allergen and diluent injections. The role of activin-A, a cytokine induced in allergic and tissue repair processes, on the chemotactic profiles of DC subsets was also examined. Plasmacytoid (pDCs) and conventional DCs (cDCs) were evaluated at various time-points in the blood and skin. In situ activin-A expression was assessed in the skin and its effects on chemokine receptor expression of isolated cDCs were investigated. Blood pDCs were reduced 1 h after challenge, while cDCs decreased gradually within 24 h. Skin cDCs increased significantly 24 h after the first challenge, inversely correlating with blood cDCs. Activin-A in the skin increased 24 h after the first allergen challenge and correlated with infiltrating cDCs. Activin-A increased the CCR10/CCR4 expression ratio in cultured human cDCs. DC subsets demonstrate distinct kinetic profiles in the blood and skin especially during acute allergic inflammation, pointing to disparate roles depending on each phase of the inflammatory response. The effects of activin-A on modulating the chemotactic profile of cDCs suggest it may be a plausible therapeutic target for allergic diseases.
PMCID: PMC4022198  PMID: 24877070
4.  Osteopontin has a crucial role in allergic airway disease through regulation of dendritic cell subsets 
Nature medicine  2007;13(5):570-578.
Osteopontin (Opn) is important for T helper type 1 (TH1) immunity and autoimmunity. However, the role of this cytokine in TH2-mediated allergic disease as well as its effects on primary versus secondary antigenic encounters remain unclear. Here we demonstrate that OPN is expressed in the lungs of asthmatic individuals and that Opn-s, the secreted form of Opn, exerts opposing effects on mouse TH2 effector responses and subsequent allergic airway disease: pro-inflammatory at primary systemic sensitization, and anti-inflammatory during secondary pulmonary antigenic challenge. These effects of Opn-s are mainly mediated by the regulation of TH2-suppressing plasmacytoid dendritic cells (DCs) during primary sensitization and TH2-promoting conventional DCs during secondary antigenic challenge. Therapeutic administration of recombinant Opn during pulmonary secondary antigenic challenge decreased established TH2 responses and protected mice from allergic disease. These effects on TH2 allergic responses suggest that Opn-s is an important therapeutic target and provide new insight into its role in immunity.
PMCID: PMC3384679  PMID: 17435770
5.  Activin-A induces regulatory T cells that suppress T helper cell immune responses and protect from allergic airway disease 
The Journal of Experimental Medicine  2009;206(8):1769-1785.
Activin-A is a pleiotropic cytokine that participates in developmental, inflammatory, and tissue repair processes. Still, its effects on T helper (Th) cell–mediated immunity, critical for allergic and autoimmune diseases, are elusive. We provide evidence that endogenously produced activin-A suppresses antigen-specific Th2 responses and protects against airway hyperresponsiveness and allergic airway disease in mice. Importantly, we reveal that activin-A exerts suppressive function through induction of antigen-specific regulatory T cells that suppress Th2 responses in vitro and upon transfer in vivo. In fact, activin-A also suppresses Th1-driven responses, pointing to a broader immunoregulatory function. Blockade of interleukin 10 and transforming growth factor β1 reverses activin-A–induced suppression. Remarkably, transfer of activin-A–induced antigen-specific regulatory T cells confers protection against allergic airway disease. This beneficial effect is associated with dramatically decreased maturation of draining lymph node dendritic cells. Therapeutic administration of recombinant activin-A during pulmonary allergen challenge suppresses Th2 responses and protects from allergic disease. Finally, we demonstrate that immune cells infiltrating the lungs from individuals with active allergic asthma, and thus nonregulated inflammatory response, exhibit significantly decreased expression of activin-A's responsive elements. Our results uncover activin-A as a novel suppressive factor for Th immunity and a critical controller of allergic airway disease.
PMCID: PMC2722168  PMID: 19620629

Results 1-5 (5)