Photomicrographs of CRS specimens stained with Hematoxylin & Eosin (left) or stained for eosinophil major basic protein (MBP) by immunofluorescence (right). On the left the figure demonstrates eosinophilic inflammation in tissue (lower part of image), eosinophil clusters (black arrows) in mucus, subepithelial basement membrane thickening and damaged epithelium (yellow arrows) (original magnification x 160).  On the right the serial section shows that MBP in subepithelial tissue is contained within the cells or in intact granules (punctate staining) outside the cells. In mucus, diffuse MBP staining is in eosinophil clusters (white arrows) and outside of clusters (anti MBP, original magnification x 160).

© 2005 American Academy of Allergy, Asthma and Immunology, Ponikau JU, Sherris DA, Kephart GM, Kern EB, Congdon DJ Adolphson CR, Springett MJ, Gleich GJ, Kita H: Striking deposition of toxic eosinophil major basic protein in mucus: implications for chronic rhinosinusitis. Journal of Allergy and Clinical Immunology 2005 Aug; 116(2):362-9.