Identification of particular epithelial areas and cells that transport polypeptide-coated nanoparticles in the nasal respiratory mucosa of the rabbit

The active transcytosis of many different polypeptides (either presented fr ee or adsorbed on latex nanoparticles), found in the respiratory mucosa of the upper nasal concha, has previously been shown to be proportional to the total volume of the lymphoid aggregates present in the tissue. By combinin g the use of fluorescent nanoparticles, flux measurements, confocal and sca nning electron microscopy and conventional histology, it is shown in this p aper that: (i) the areas of epithelium overlying lymphoid aggregates are th e only transporting polypeptides; (ii) the respiratory epithelium in these areas consists mainly of non-ciliated microvillar cells, with numerous cili ated cells and rare mucous goblet cells at the periphery of the area only; (iii) non-ciliated microvillar cells are distinguishable in cells with well developed finger-like microvilli and cells with an irregularly pleated api cal membrane, similar to that of intestinal and bronchial antigen-sampling M-cells; (iv) groups of polypeptide-coated nanospheres are found bound to t his latter type of cells, demonstrating that these are the transporting cel ls, detected at the first stage of the transcytotic cycle. (C) 1999 Elsevie r Science B.V. All rights reserved.