Age Related Histochemical Changes in Thymus, Spleen and Mesenteric Lymph Nodes in Mice, Rat and Guinea Pig

The study was designed to observe the histochemical changes in the thymus, spleen and mesenteric lymph nodes in prenatal and postnatal age groups of mice, rat and guinea pigs. Materials for the present study were collected from six animals each in all the age groups of all the species. Tissue pieces were collected and frozen sections of 15 to 20 microns were used for the present study. In thymus, the free reticulo-epithelial cells, those involved in formation of Hassall's corpuscles and macrophages were PAS positive. Some of the Hassall's corpuscles were Alcian blue positive only in mice. The reticulo-epithelial cells and macrophages showed a positive reaction for Acid phosphatase. Alkaline phosphatase activity was found to be absent in all the species. In spleen, the capsule, trabeculae and vascular network were PAS positive. Reticular cells and macrophages showed and Acid phosphatase reaction. In mesenteric lymph nodes, the macrophages were positive for PAS and Acid phosphatase activity in all the age groups studied.