[Analysis of the cellular infiltrate and epithelial class I and II molecular expression in edematous type nasal...

Although in the last few years histopathological, immunohistochemical and immunological studies on nasal polyps have been carried out by several Authors, the etiology of these formations still remains unknown. Nasal polyps have a very characteristic structure and have been classified in three histologic types: edematous, glandular and fibrous. In the present report, 11 nasal polyps of edematous type, representing 61% of total number of collected polyps, were studied employing immunohistochemical methods. All the examined polyps were similar in histology and positivity pattern for HLA molecule expression. The edematous core appeared infiltrated (149 cells/mm.2) mainly by eosinophils (> 90%), whereas the peripheral subepithelial connective tissue contained cellular clusters (416 cells/mm2.) made up of different subsets of hematic cells (30.8% were monocytes-macrophages and 48.6% were lymphocytes largely represented by CD4+ cells). On the contrary, mast cells were quite rare (on the average 1.7 cells/mm2.) and located near T cell clusters. The epithelial positivity for HLA-DR and HLA-A,B,C molecules showed a characteristic discontinuous pattern. In the same patient, controlateral nasal mucosa showed a histological structure very similar to that of polyps. The above data suggest that the presence of polyps is the result of an inflammatory process brought about by a complex array of cellular and humoral components.