O’Neil et al. Allergy, Asthma & Clinical Immunology 2010, 6:28 http://www.aacijournal.com/content/6/1/28 be the case for s-OPN. The expression of OPN in the nasal lavage fluid of AR patients should be measured to determine if soluble OPN expression is changed by natural pollen exposure or glucocorticoids. In the lower airways, Takahashi et al [10] found that although there was no dif- ference in intracellular OPN expression in the lung, there was a significant increase in the sputum OPN levels between asthmatic and healthy subjects. Conversely, Xanthou et al [11] reported an increased intracellular OPN expression in asthmatics, compared to healthy subjects. It has been previously seen that glucocorticoids are quite effective in inhibiting both the expression of inflammatory cells and clinical symptoms [3] induced by the pollen season. It has previously been shown that FOXP3, GATA-3 [5] and EG2+ cells [2] in the nasal mucosa of AR patients increase during the pollen season and that their expression is suppressed by the nasal glu- cocorticosteroid FP. Unlike the previous biopsy studies and murine studies [14] the expression of OPN was not inhibited by treatment with FP. This lack of inhibition of OPN expression has also been observed in the serum, bronchial tissue and bronchoalveolar lavage fluid of asthmatics [16]. Erin et al [3] has previously shown that FP is effective in inhibiting Th2, but not Th1, cytokine synthesis. OPN has been suggested to act as both a Th1 and Th2 cytokine [8]. The lack of effect by FP on the OPN in the nasal mucosa could suggest that intracellu- lar OPN has a Th1-like role in the nasal mucosa of AR. Conclusions In conclusion, despite the large role that OPN plays in many diseases, including Th2 diseases, like asthma, OPN in allergic rhinitis has been shown here to not be directly involved in the nasal mucosa changes over the pollen season, or in the response to glucocorticoid treat- ment. This suggests that intracellular OPN in AR patients cannot be used as a marker of disease. Acknowledgements We would like to acknowledge the assistance of Julia Fernandez-Rodriguez and Esbjörn Telemo for their expert advice and use of equipment. We would like to thank Margareta Sjöstrand for proofing the manuscript. Author details 1Krefting Research Centre, Sahlgrenska Academy, University of Gothenburg, Sweden. 27th Respiratory Department, Athens Chest Hospital (“Sotiria”), Greece. Authors’ contributions SO performed the immunohistochemistry and analyses, and drafted the manuscript. KS and CM helped in design of experiment. AB and JO conceived of the study. JO and KS helped draft the manuscript. TP provided the data from a previous eosinophils study. All authors read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Page 4 of 4 Received: 17 June 2010 Accepted: 2 November 2010 Published: 2 November 2010 References 1. Skoner DP: Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis. J Allergy Clin Immunol 2001, 108:S2-8. 2. Pullerits T, Praks L, Ristioja V, Lotvall J: Comparison of a nasal glucocorticoid, antileukotriene, and a combination of antileukotriene and antihistamine in the treatment of seasonal allergic rhinitis. J Allergy Clin Immunol 2002, 109:949-955. 3. Erin EM, Zacharasiewicz AS, Nicholson GC, Tan AJ, Higgins LA, Williams TJ, Murdoch RD, Durham SR, Barnes PJ, Hansel TT: Topical corticosteroid inhibits interleukin-4, -5 and -13 in nasal secretions following allergen challenge. Clin Exp Allergy 2005, 35:1608-1614. 4. Holm A, Dijkstra M, Kleinjan A, Severijnen LA, Boks S, Mulder P, Fokkens W: Fluticasone propionate aqueous nasal spray reduces inflammatory cells in unchallenged allergic nasal mucosa: effects of single allergen challenge. J Allergy Clin Immunol 2001, 107:627-633. 5. Malmhall C, Bossios A, Pullerits T, Lotvall J: Effects of pollen and nasal glucocorticoid on FOXP3+, GATA-3+ and T-bet+ cells in allergic rhinitis. Allergy 2007, 62:1007-1013. 6. Sergejeva S, Malmhall C, Lotvall J, Pullerits T: Increased number of CD34+ cells in nasal mucosa of allergic rhinitis patients: inhibition by a local corticosteroid. Clin Exp Allergy 2005, 35:34-38. 7. Kunii Y, Niwa S, Hagiwara Y, Maeda M, Seitoh T, Suzuki T: The immunohistochemical expression profile of osteopontin in normal human tissues using two site-specific antibodies reveals a wide distribution of positive cells and extensive expression in the central and peripheral nervous systems. Med Mol Morphol 2009, 42:155-161. 8. Lund SA, Giachelli CM, Scatena M: The role of osteopontin in inflammatory processes. J Cell Commun Signal 2009, 3:311-322. 9. Kohan M, Bader R, Puxeddu I, Levi-Schaffer F, Breuer R, Berkman N: Enhanced osteopontin expression in a murine model of allergen- induced airway remodelling. Clin Exp Allergy 2007, 37:1444-1454. 10. Takahashi A, Kurokawa M, Konno S, Ito K, Kon S, Ashino S, Nishimura T, Uede T, Hizawa N, Huang SK, Nishimura M: Osteopontin is involved in migration of eosinophils in asthma. Clin Exp Allergy 2009, 39:1152-1159. 11. Xanthou G, Alissafi T, Semitekolou M, Simoes DC, Economidou E, Gaga M, Lambrecht BN, Lloyd CM, Panoutsakopoulou V: Osteopontin has a crucial role in allergic airway disease through regulation of dendritic cell subsets. Nat Med 2007, 13:570-578. 12. Lu X, Zhang XH, Wang H, Long XB, You XJ, Gao QX, Cui YH, Liu Z: Expression of osteopontin in chronic rhinosinusitis with and without nasal polyps. Allergy 2009, 64:104-111. 13. Puxeddu I, Berkman N, Ribatti D, Bader R, Haitchi HM, Davies DE, Howarth PH, Levi-Schaffer F: Osteopontin is expressed and functional in human eosinophils. Allergy 2010, 65:168-174. 14. Kurokawa M, Konno S, Matsukura S, Kawaguchi M, Ieki K, Suzuki S, Odaka M, Watanabe S, Homma T, Sato M, Takeuchi H, Hirose T, Huang SK, Adachi M: Effects of corticosteroids on osteopontin expression in a murine model of allergic asthma. Int Arch Allergy Immunol 2009, 149(Suppl 1):7-13. 15. Simoes DC, Xanthou G, Petrochilou K, Panoutsakopoulou V, Roussos C, Gratziou C: Osteopontin deficiency protects against airway remodeling and hyperresponsiveness in chronic asthma. Am J Respir Crit Care Med 2009, 179:894-902. 16. Samitas K, Zervas E, Vittorakis S, Semitekolou M, Alissafi T, Bossios A, Gogos H, Economidou E, Lotvall J, Xanthou G, Panoutsakopoulou V, Gaga M: Osteopontin expression and relation to disease severity in human asthma. Eur Respir J 2010. 17. Wang KX, Denhardt DT: Osteopontin: role in immune regulation and stress responses. Cytokine Growth Factor Rev 2008, 19:333-345. 18. Shinohara ML, Lu L, Bu J, Werneck MB, Kobayashi KS, Glimcher LH, Cantor H: Osteopontin expression is essential for interferon-alpha production by plasmacytoid dendritic cells. Nat Immunol 2006, 7:498-506. doi:10.1186/1710-1492-6-28 Cite this article as: O’Neil et al.: Quantitative expression of osteopontin in nasal mucosa of patients with allergic rhinitis: effects of pollen exposure and nasal glucocorticoid treatment. Allergy, Asthma & Clinical Immunology 2010 6:28.