M-cells in the epithelium of the nasopharyngeal tonsil.

Electron-microscope investigation on the epithelium was carried out in 23 nasopharyngeal tonsils. Adenoidectomy was performed on the ground of recurrent adenoiditis in the interattacks period in 13 boys and 10 girls between the ages of 2 to 4. The presence of five characteristic cellular types was found on the surface of the adenoid epithelium: tall cylindrical ciliated cells; cylindrical cells covered only with microvilli; secretory cells with the predominance of the so-called "dark granules"-producing cells; flat epithelial cells; cubic cells with microvilli on the surface and many vesicles in the cytoplasm. The last type of cells rank together with the M-cells, described by Owen and Jones in the epithelium of Peyer's patches in human beings and found in the palatal tonsil by various authors. A discussion is made on the pinocytary and secretory activity of the M-cells that is being linked with the immunogenesis of the nasopharyngeal tonsil. It is pointed out that in normal conditions the reticulation of the epithelium of the adenoid is found only in the zones that had their surface covered by M-cells.