Cytolytic effects of glucocorticoid on thymus-medullary lymphocytes incubated in vitro

Abstract Thymus cortical and medullary lymphocytes (TCL and TML) were incubated in vitro with or without cortisol. The cytolytic effects of the steroid on both thymocytes were examined in the microscope and by measurements of protein and RNA synthetic activities. There did not appear to be significant differences in the extent of damage by glucocorticoid exposure between both thymocytes, although the reduction of RNA synthesis in TML was less marked as compared with that in TCL. The facts that lymphocytes in thymus medulla were able to survive after cortisone injection and that the cells incubated in vitro were affected by the steroid presented the hypothesis that there might be some particular mechanisms in thymus medulla to protect lymphocytes from the cytolytic action of glucocorticoid.