T cell proliferation. The T cell proliferation was assessed by CFSE-dilution assay. A1-A4, the histograms indicate the T cell proliferation. The numbers indicate the frequency of proliferating T cells. A5 is an isotype control. B, the bars indicate the summarized data of A1-A4. The data in the bar graph were presented as mean ± SD. *, p < 0.01, compared with group A1. The data represent 3 separate experiments.