In seven monkeys (6 Macaca fascicularis, 1 M. mulatta; 2.4 +/- 0.6 kg in weight) the labial and buccal mucosae were studied morphologically and quantitatively. Following fixation by perfusion, the upper and lower lips and entire cheeks were dissected free and processed for light-, scanning and transmission electron microscopy. Established programs (HISTOMEP, MUMANA II) and appropriate morphometric techniques were used to estimate, at the light-microscopic level, the epithelial thickness, the width of the combined lamina propria/submucosa, and the volumetric composition of the gland-containing portions of lip and cheek mucosae. The cheek epithelium was more than twofold thicker than the lip epithelium, on the average 0.46 +/- 0.04 and 0.21 +/- 0.02 mm, respectively, with no differences related to sex or topographical sites. The combined lamina propria/submucosa was 1.32 +/- 0.19 and 1.50 +/- 0.26 mm in width in cheeks and lips, respectively. The main mucosal constituents at both sites were glandular and connective tissue, and lymph follicles associated with secretory ducts. In lips, the volume of plasma cells around gland acini correlated positively with the amount of lymphoid tissue present around topographically related ducts. It is suggested that the duct/lymph follicle assembly may serve as a local antigen-recognition system.

In three mature monkeys (Macaca fascicularis; 3.5 +/- 0.3 kg in weight), the labial, buccal and soft-palate mucosae were examined morphologically and stereologically. Using fixation by perfusion, standardized methods of tissue preparation and morphometric analysis at the light-microscopic level, the gross dimensions (i.e., epithelial thickness, width of combined lamina propria/submucosa) and the volumetric composition of the oral mucosae were estimated and compared with those of young animals examined previously. The data show (1) an age-related decline in the volume and prevalence of organized lymphoid tissue (i.e., lymphoid follicles associated with secretory ducts), (2) a stable plasma-cell density in the interglandular connective tissue, and (3) an increase of glandular tissue in mature versus young animals. It is suggested that the lymphoid follicles associated with secretory ducts, providing for plasma-cell generation, mirror the tonsillar lymphoid tissue declining after puberty.