Evidence of ZIO positive Langerhans cell: a dendritic cell subset in normal and polypoid nasal mucosa

Nasal polyps are outgrowths of oedematous nasal mucosa of inflammatory origin. Langerhans cells (LCs) residing in the nasal mucosa are responsible for maintaining the immunological environment. This study aims to ascertain the distribution of zinc iodide osmium (ZIO) positive LCs in normal nasal mucosa, and to compare the same with that in polypoid mucosa. Normal nasal mucosa obtained from patients undergoing septoplasty (n=21) and polypoid mucosa (n=21) obtained from patients with sinonasal polyposis due to diffuse sinonasal inflammation or allergic fungal rhinosinusitis were processed for identification of LCs using the ZIO technique. The number of ZIO positive LCs were counted per unit area of lamina propria and statistically analysed. The ZIO positive LCs were seen in the epithelium, lamina propria and among the glands. Both dendritic and non-dendritic LCs were present. They were noted within the lymphatic aggregations in the lamina propria, and were also noted in and around the blood vessels. The ZIO positive LCs were present in both normal and polypoid nasal mucosa. The median number of ZIO positive LCs was 0 (range: 0-1) per mm2 and 12 (range: 0-44) per mm2 in the normal and polypoid groups, respectively. This difference was statistically significant (p=0.001). No significant difference was noted based on the aetiology of the polyps. This is the first report of the presence of ZIO positive LCs in the nasal mucosa. Their significantly higher number in nasal polyps suggests an immunological role in the presence of inflammation.