CD25 content variation with the responses of T helper cell to IL-2 induced proliferation

Objective To elucidate the expression diversity of IL-2R subunits in T helper(Th) cells under different activation condition and clarify its relationship with the response to IL-2 induced proliferation.Methods In vitro cultured Th1 cells were activated by plate bound anti-mouse CD3 McAb.In both activated and inactivated Th1 cells the expression of different IL-2R subunit was evaluated by real-time PCR and fluorescence staining,3H incorporation assay was adopt to measure the proliferation of the cells in response to IL-2 treatment,IL-2 affinity was determined via I125 labeled IL-2.IL-2Rα siRNA transfection was applied to knockdown CD25 expression in activated Th1 cells and its effect was confirmed by Western blot,IL-2 induced proliferation in IL-2Rα siRNA transfected Th1 cells were subsequently detected.CD4 cells were isolated from na(i)ve BALB/c mice and were also stimulated by plate bound anti-CD3 McAb.Cells were harvested at different days posterior to the stimulation,CD25 content and IL-2 induced proliferation were determined by flow cytometry and 3H incorporation assay respectively.Results In comparison with inactivated cells,only the expression of CD25but not other IL-2R subunits was significantly increased in activated Th1 cells.In accordance with elevated CD25,IL-2 affinity was also increased in activated Th1 cells,however,which resulted in decreased cell proliferation in response to IL-2 treatment.In activated Th1 cells,when CD25 expression was differently knockdown by different-dosed IL-2Rα siRNA transfection,the highest IL-2 response was observed in the cells with partially CD25 depression.Forin vitro activated na(i)ve CD4 cells the elevated CD25 expression gradually decreased and the highest proliferation response was detected at day 8 post stimulation upon IL-2 treatment.Conclusion Although CD25 is necessary for IL-2 induced proliferation,however,the excessively expressed CD25 lead to lower proliferation response.Not fully activated Thl or CD4 cells,but partially activated cells with lightly increased CD25 content possessed highest proliferation rate in response to IL-2 treatment. Key words: CD25; IL-2; T helper cells; Proliferation