Orosomucoid like 3 (ORMDL3) has been strongly linked with asthma in genetic association studies, but its function in asthma is unknown. We demonstrate that in mice ORMDL3 is an allergen and cytokine (IL-4 or IL-13) inducible endoplasmic reticulum (ER) gene expressed predominantly in airway epithelial cells. Allergen challenge induces a 127-fold increase in ORMDL3 mRNA in bronchial epithelium in WT mice, with lesser 15-fold increases in ORMDL-2 and no changes in ORMDL-1. Studies of STAT-6–deficient mice demonstrated that ORMDL3 mRNA induction highly depends on STAT-6. Transfection of ORMDL3 in human bronchial epithelial cells in vitro induced expression of metalloproteases (MMP-9, ADAM-8), CC chemokines (CCL-20), CXC chemokines (IL-8, CXCL-10, CXCL-11), oligoadenylate synthetases (OAS) genes, and selectively activated activating transcription factor 6 (ATF6), an unfolded protein response (UPR) pathway transcription factor. siRNA knockdown of ATF-6α in lung epithelial cells inhibited expression of SERCA2b, which has been implicated in airway remodeling in asthma. In addition, transfection of ORMDL3 in lung epithelial cells activated ATF6α and induced SERCA2b. These studies provide evidence of the inducible nature of ORMDL3 ER expression in particular in bronchial epithelial cells and suggest an ER UPR pathway through which ORMDL3 may be linked to asthma.

Basophils are thought to play pivotal roles in allergic inflammation through rapid release of chemical mediators in addition to sustained production of Th2 cytokines, including IL-4. A newly identified cytokine, IL-33, has been recognized as one of the key cytokines enhancing Th2-balanced immune regulation through its receptor, ST2. The present study was conducted to elucidate whether IL-33 acts directly on, and affects the functions of, human basophils. Real-time PCR analysis showed that basophils express transcripts for ST2. The expression levels were significantly higher compared with eosinophils and neutrophils, and treatment with IL-33 significantly up-regulated basophil ST2 mRNA expression. Expressions of IL-4 and IL-13 mRNA were also up-regulated by IL-33, and there was also enhanced secretion of IL-4 protein. IL-33 increased the surface levels of basophil CD11b expression and enhanced basophil adhesiveness. Although IL-33 failed to directly induce degranulation or attract basophils, it exerted priming effects on basophils. It enhanced degranulation in response to IgE-crosslinking stimulus and also enhanced basophil migration toward eotaxin without changing surface CCR3. Also, IL-33 synergistically enhanced IL-4 production and CD11b expression by IL-3-stimulated basophils. Neutralization using Ab specific for ST2 significantly diminished the enhancing effects of IL-33 on both basophil CD11b expression and migration toward eotaxin, indicating that IL-33 signals via ST2 expressed on basophils. This study revealed that IL-33 potently regulates migration and activation of human basophils. IL-33 may be a key cytokine in the pathogenesis of Th2-dominant inflammation by acting not only on lymphocytes but also on effector cells such as basophils.

ORMDL3 (orosomucoid like 3) has been strongly linked with asthma in genetic association studies. As allergen challenge induces lung ORMDL3 expression in WT mice, we have generated human ORMDL3 Zona Pellucida 3 Cre (hORMDL3zp3-Cre) mice that overexpress human ORMDL3 universally to investigate the role of ORMDL3 in regulating airway inflammation and remodeling. These hORMDL3zp3-Cre mice have significantly increased levels of airway remodeling including increased airway smooth muscle, subepithelial fibrosis, and mucus. hORMDL3zp3-Cre mice had spontaneous increased AHR to methacholine compared to WT mice. This increased airway remodeling was associated with selective activation of the Unfolded Protein Response pathway transcription factor ATF6 (but not Ire1 or PERK). The ATF6 target gene SERCA2b, implicated in airway remodeling in asthma, was strongly induced in the lungs of hORMDL3zp3-Cre mice. In addition, increased levels of expression of genes associated with airway remodeling (TGF-β1, ADAM8) were detected in airway epithelium of these mice. Increased levels of airway remodeling preceded increased levels of airway inflammation in hORMDL3zp3-Cre mice. hORMDL3zp3-Cre mice had increased levels of IgE, with no change in levels of IgG, IgM, and IgA. These studies provide evidence that ORMDL3 plays an important role in vivo in airway remodeling potentially through ATF6 target genes such as SERCA2b, and/or through ATF6 independent genes (TGF-β1, ADAM8).

Mycobacteria possess various immunomodulatory molecules on the cell wall. Mannose-capped lipoarabinomannan (Man-LAM), a major lipoglycan of Mycobacterium tuberculosis, has long been known to have both inhibitory and stimulatory effects on host immunity. However, the direct Man-LAM receptor that explains its pleiotropic activities has not been clearly identified. Here, we report that a C-type lectin receptor Dectin-2 (gene symbol Clec4n) is a direct receptor for Man-LAM. Man-LAM activated bone-marrow-derived dendritic cells (BMDCs) to produce pro- and anti-inflammatory cytokines, whereas it was completely abrogated in Clec4n(-/-) BMDCs. Man-LAM promoted antigen-specific T cell responses through Dectin-2 on DCs. Furthermore, Man-LAM induced experimental autoimmune encephalitis (EAE) as an adjuvant in mice, whereas Clec4n(-/-) mice were resistant. Upon mycobacterial infection, Clec4n(-/-) mice showed augmented lung pathology. These results demonstrate that Dectin-2 contributes to host immunity against mycobacterial infection through the recognition of Man-LAM.