Plant pollens are one of the most common outdoor allergens. Pollen grains and subpollen particles can reach lower airways and induce symptoms of seasonal asthma and allergic rhinitis. Plants possess NAD(P)H oxidase activity that generates reactive oxygen species for physiological functions such as root-hair and pollen-tube growth, defense against microbial infections and cell signaling. The presence of NAD(P)H oxidases in pollens and their role in induction of airway inflammation have not been described until recently.
We discovered the presence of NAD(P)H oxidase in ragweed and other plant pollens. These oxidases induce reactive oxygen species in mucosal cells (signal 1) independent of adaptive immunity. This reactive oxygen species facilitates antigen (signal 2)-induced allergic inflammation. Inhibiting signal 1 by administration of antioxidants attenuated ragweed extract-induced allergic inflammation. Likewise, abrogating signal 2 by antigen challenge in mice lacking T cells failed to induce allergic inflammation.
Reactive oxygen species generated by pollen NAD(P)H oxidase play a major role in pathogenesis of allergic airway inflammation and airway hypersensitivity. Based on our findings, we propose a ‘two signal hypothesis of allergic inflammation’ in which both signal 1 (reactive oxygen species) and signal 2 (antigen presentation) are required in order to induce full-blown allergic inflammation.
aNHLBI Proteomics Center, Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA
bDepartment of Microbiology and Immunology, Sealy Center for Molecular Medicine, University of Texas Medical Branch, Texas, USA
cDivision of Allergy Pulmonary Immunology Critical Care and Sleep, Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas, USA
Correspondence to Sanjiv Sur, MD, Divisions of Allergy Pulmonary Immunology Critical Care and Sleep, Departments of Internal Medicine, Microbiology & Immunology, Biochemistry & Molecular Biology, University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-1083, USA Tel: +1 409 772 3410; e-mail: firstname.lastname@example.org