K. Roongrotwattanasiri 1,2, R. Pawankar1, S. Kimura1, S. Mori1, T.Yagi.1
1. Rhinology and Allergy, Nippon Medical School, Tokyo 113-8603, Japan.
2. Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
Introduction: The pathogenesis of chronic rhinosinusitis with nasal polyposis (NP) is still not well defined. Previously, we have shown an important role for eosinophils and mast cells in the pathogenesis of NP. Additionally, Th2 type cells are increased and play an important role irrespective of the patient’s atopic status. In this context, we have shown high levels of TARC and TSLP, eotaxin, RANTES in NP. Forkhead box P3 (FOXP3) plays a key role in CD4+CD25+ regulatory T cell function and represents a specific marker for these cells. To evaluate the role of regulatory T cells (Treg) in the pathogenesis of nasal polyposis, we analyzed the numbers of FOXP3+ cells in nasal polyps versus nasal mucosa from patients with allergic rhinitis (AR).
Materials and Method FOXP3 expression in the nasal mucosa of 15 patients with AR and nasal polyp tissue from 17 patients with chronic rhinosinusitis with NP were analyzed by immunohistochemistry. Results are expressed as the number of positively stained cells in the epithelial and subepithelium layer. Statistical Data analysis was done using the Student t-test at 95% interval and a P value of less than 0.05 was accepted as indicating a statistically significant difference.
Results The number of FOXP3+ cells in the subepithelium of nasal polyps was significantly lower than that in the nasal mucosa of AR patients (2.79 and 5.99 respectively, p=0.002). No difference was noted in the number of FOXP3+ cells in epithelium ( 3.60 and 2.35 respectively) of nasal polyps and nasal mucosa (p=0.130). Therefore, the numbers of T reg cells were significantly lower in nasal polyps than in the nasal mucosa of patients with AR.
Conclusion Nasal polyps have lower numbers of T reg cells (FOXP3 expression) as compared to the nasal mucosa of AR patients. Since the severity of eosinophilic, Th2 type inflammation and levels of inflammatory mediators are much higher in NP than in the nasal mucosa of AR patients, this may reflect an inverse co-relation with these factors and could explain at least in part the more pronounced structural alterations in NP. Further studies are needed to confirm this.