THE HUMAN ADENOID - A MORPHOLOGIC STUDY

Objective: We examined the route by which antigen on the surface of th e adenoid may be brought into contact with the lymphoid follicles in t he submucosa of the adenoid. Design: We studied under light and electr on microscopy 13 adenoids from children undergoing elective surgery. P ortions of all of the specimens were fixed in formalin and embedded in paraffin and plastic for hematoxylin-eosin and periodic acid-Schiff s taining. Portions of four adenoids were fixed in glutaraldehyde for el ectron microscopy. Results: Two major types of epithelium were evident by light microscopy: a ciliated or squamous epithelium containing few lymphocytes and a nonciliated-flat epithelium with a heavy infiltrati on of lymphocytes (''lymphoepithelium''). Scanning microscopy showed t he surface of this lymphoepithelium to be composed largely of cells wi th multiple microfolds known as M-cells. Freeze-fracture technique sho wed many lymphocytes under the M-cells. Transmission electron microsco py showed the lymphocytes to be located in compartments formed by the epithelial cells. Light microscopy study of 50 serial sections embedde d in plastic suggested that the compartments communicated to form intr aepithelial channels for the lymphocytes. Conclusion: The epithelium o f the adenoid has areas with ciliated epithelium adjacent to areas wit h epithelium containing M-cells and intraepithelial lymphatic channels . Hypothesis: The lymphoepithelium of the adenoid is a mechanism for t ransporting antigen via the M-cells to the underlying lymphoid follicl es.