A Qualitative and Quantitative Morphologic Study of Peyer's Patches of the Mouse

Abstract

Peyer's patches of adult mice were morphologically studied by light microscopy.The patch is topographically divided into four portions: germinal center, follicular area, parafollicular area and dome area. The germinal center consists of light and dark zones. The follicular area surrounds the germinal center, especially the light zone which has an apical pole directed toward the mucosal surface. The parafollicular area surrounds the follicular area and contains postcapillary venules with high endothelium. The dome area is situated just above the follicular area. The epithelium over the dome area is infiltrated with numerous lymphocytes.Quantitatively, the germinal center, follicular area and parafollicular area are almost similar in volume (about 30%) and the dome area constitutes only a small portion (about 10%). The density of small lymphocytes is highest in the follicular area and lowest in the germinal center. Out of the total small lymphocytes in the patch, 8.4% are included in the germinal center; 58.2% in the follicular area; 26.7% in the parafollicular area; and 3.8% in the dome area. Intraepithelial small lymphocytes are almost twice as abundant in the dome as in the villi. In the dome, almost half the intraepithelial lymphocytes are above the nuclear level of the epithelial cells, whereas in the villi 7.3% of intraepithelial lymphocytes are above the nuclear level.The results suggest that the functional structure of the Peyer's path is similar to that of peripheral lymphatic tissues.