10 - Microenvironment of the Rat Thymus after Cyclosporin Treatment

Abstract

This chapter presents a comprehensive study to elucidate the changes of all types of thymic nonlymphoid cells induced by cyclosporin (CS) and the interplay between thymic lymphoid and nonlymphoid cells. For this study, male 6-week-old Wistar rats with an average body weight of 145 g at the beginning of the experiment were used. The changes of all types of thymic epithelial cells were studied after the application of CS by using the immunohistochemical methods with various monoclonal antibodies such as OX-6 (anti-Ia), KII, K8, K8.13 (panepithelial), K19, R-MC 20 (subcapsular/medullary epithelium), and KL1 (subset of medullary epithelial cells). The study found that the application of CS to rats induced prominent changes of all types of thymic nonlymphoid cells. Thymic cortical epithelial network became denser and coarser, and cortical epithelial cells became stocky with coarse cellular prolongations. The subcapsular epithelial cells, although phenotypically dissimilar from cortical epithelium, changed in a very similar manner. Cortical macrophages became enlarged and rounded, but their number did not increase. Phenotypically, they become similar to macrophages of the corticomedullary zone. Considering that after CS treatment the expression of prostaglandin synthase is increased, it is very likely that cortical macrophages become engaged in the production of arachidonic acid metabolites, similarly to macrophages of the corticomedullary zone of the normal thymus.