Objective:To investigate the influence of IL-2 on the apoptosis of activated and inactivated lymphocytes.Methods:Selected an appropriate system as the model of activated lymphocytes by detecting the expression of Fas and FasL in two systems of one way MLR using RT-PCR. Detected the apoptosis of activated and inactivated lymphocytes after the stimulation of IL-2 with the methods of FITC-Annexin-V/PI staining.The resultaint change of membrane Fas was evaluated by FACS,and the lymphocytes from doner and acceptor were distinguished by CFSE staining.Results:To the inactivated spleen lymphocytes, exogenous IL-2 inhibited their apoptosis and the expression of Fas; while to the spleen lymphocytes activated by mixed lymphocyte reaction, exogenous IL-2 promoted their apoptosis and upregulated the expression of Fas, which did the same both to the doner cells and the acceptor cells.Conclusion:IL-2 can inhibit the apoptosis of inactivated lymphocytes, and promote the apoptosis of activated lymphocytes.These effects have something to do with the change of expression of Fas.