Inhibitory effect of cyclosporin A on T lymphocyte DNA synthesis

The interference of Cyclosporin A (CyA) with peripheral lymphocytes DNA synthesis was investigated. The results showed that the drug could strongly inhibit T cell proliferation in response to PHA stimulation if added at the start or at the early phase of the process, and it failed to do so if added 48 h later when most cells had already started to proliferate. Without PHA, no obvious differences were detected between normal control and CyA-treated cells. A comparison was made between T cell DNA synthesis of peripheral blood lymphocytes of healthy volunteers and renal transplant patients. It was found that T-cell DNA synthesis of patients was significantly lower than that of the healthy controls. From the above it may be suggested that CyA activity on T cell proliferation is similar in vivo and in vitro.