Histological, immunohistochemical, and morphometric study on the postnatal development of Peyer’s patches in albino rat

Introduction Peyer’s patches (PPs) are essential elements of the gut-associated lymphatic tissue that are involved in defense against pathogens that may be colonizing the gut and are also involved in oral food tolerance otherwise food allergy occurs. Aim This research aimed to study the postnatal development of PPs in male albino rats. Materials and methods Fifty male albino rats were divided into five groups of 10 animals each. Group 1 (1 day old), group 2 (1 week old), group 3 (2 weeks old), group 4 (4 weeks old), and group 5 (8 weeks old). The terminal part of the ileum was dissected out and processed for light and electron microscopic examinations. Paraffin sections were stained with hematoxylin and eosin, periodic acid-Schiff and immunohistochemical staining was carried out for detection of CD3 and CD20 (markers of T and B lymphocytes, respectively). Quantitative morphometric study was conducted, and the results were statistically analyzed. Results Early during postnatal period, PPs appeared as small epithelial elevations overlying small aggregates of lymphocytes. The size of PPs and lymphocytic cell density increased gradually to reach maximum by adult age (group 5). Most of the lymphocytes were of the T type early postnatally followed by increase in B lymphocytes during the following age groups. Germinal centers started to appear in group 4 and in the adult age group. The epithelium covering the surface of PPs showed reduced number of goblet cells, and M cells started to appear from the age of 2 weeks onward. Conclusion Epithelium covering the PPs showed structural changes matching with functional specialization such as gradual reduction of goblet cells and appearance of M cells. In addition, an association was found between the times of onset of M cells and B-lymphocytic follicles in PPs.