الفهرس Only 14 pages are availabe for public view
 |  | from | 244 |  |  |
| | | from | 244 | | |
Abstract
Peyer’s patches are essential elements of the GALT that are involved in defense against pathogens that may be colonizing the gut and also involved in oral food tolerance otherwise food allergy occurs. Peyer’s patches are described as lymphoid cell aggregates that are found in the mucosa and submucosa along the length of the small intestine especially the ileum.
The development of Peyer’s patches is a complex process requiring interactions between the gut epithelium, antigen presenting cells (dendritic cells), high endothelial venules and lymphoid cells.
The aim of this work was to study the development of Peyer’s patches in postnatal life of male albino rats till the adult age.
Fifty male albino rats were used in the present study. Animals were divided into five equal groups (ten animals each) according to age (Group I - one day, Group II - one week, Group III - two weeks, Group IV - four weeks and Group V - eight weeks). The animals were scarified, terminal parts of their ileum were taken and prepared for examination by SEM and histological sections were prepared for light microscopic examination by different techniques of histological, histochemical, and immunohistochemical staining. Also, ultrathin sections were prepared for examination by TEM for demonstration of FAE. Morphometry and statistical analysis were done for results of each group.
Results of the present study revealed that in Group I rats, the primitive Peyer’s patches were identified by light microscopic examination as small dome shaped epithelial elevations; each overlies a small aggregate of lymphocytes. The primitive Peyer’s patches were populated mainly with T lymphocytes, while B lymphocytes were occasionally found and represented a minority.
High endothelial venules were detected in all the studied age groups starting from one day old rats, as they most probably facilitate the passage of T lymphocytes across their walls to reach the Peyer’s patches.
Peyer’s patches in rats of group II showed an increase in patch size accompanied by a statistically significant increase in the density of lymphocytic infiltration. The number of B lymphocytes was increased markedly when compared to group I rats, however T lymphocytes were still the major type of lymphocytes found. The B lymphocytes were present in small groups among T lymphocytes but no separate zones of B and T lymphocytes were formed. The aggregates of B lymphocytes were found mainly in the upper part of the mucosa, while T lymphocytes were found basally located in the mucosa and even extending to the submucosa and reaching to muscularis externa.
The Peyer’s patches in rats of group III showed further marked increase in patch size, with significant increase in the density of lymphocytic population in mucosa and extending to submucosa when compared to group II. Moreover, Peyer’s patches at this age showed prominent primary B lymphocytic follicles separated by the diffuse T lymphocytic infiltration.
In group IV rats, an increase in the patch size and the number of lymphoid follicles was noticed, with significant increase in the density of lymphocytic infiltration especially in follicular areas. Moreover, some of the lymphoid follicles showed germinal centers. This might be explained by a strong or long exposure of Peyer’s patch’s lymphoid cells to intestinal antigens following the time of weaning.
In group V rats, no remarkable changes were noticed apart from increase in the size of Peyer’s patch and significant increase in density of lymphocytic population.
The mucosa at the site of Peyer’s patches was lacking the presence of villi and crypts in all studied age groups, instead dome shaped epithelial elevations were found.
The epithelium covering the surface of Peyer’s patches showed significantly reduced number of goblet cells when compared to neighboring villi and crypts. M cells however were detected starting from the age of two weeks onwards.
Based on the results of the present study, it is believed that many structural changes occurring during the development of Peyer’s patches follow a plan of structure-function adaptation. This might explain the gradual decrease of goblet cells, with concomitant appearance and increase of M cells to adapt for the immunological function of Peyer’s patches. Similarly, the absence of villi and crypts in the areas of Peyer’s patches indicate its weak absorptive and secretory functions when compared to other areas of the intestinal mucosa.