Abstract: Objective To observe the damage to Langerhans cells induced by UVB irradiation,and to evaluate photoprotective effect of these cells from UVB irradiation by epigallocatechin-3-gallate (EGCG).Methods Biopsy specimens were obtained from normal adult foreskin,and epidermal cells were isolated.Density gradient centrifugation and magnetic cell sorting were used simultaneously to purify Langerhans cells from the cell suspension.These cells were then divided into three groups,control (no irradiation or EGCG treatment),UVB (irradiation) and EGCG (irradiation+ECCG treatment) groups.The cells in the UVB and EGCG group were irradiated by UVB (30 mJ/cm²).After the irradiation,the UVB group was incubated with RPMI-1640 containing 10% bovine serum for 4 hours,while the EGCG group with the same medium containing 200μg/mL of EGCG for 4 hours.Another four hours after the treatment,the cells were collected for the detection of apoptosis rate by propidium iodide staining and flow cytometry.Results Exposure to UVB (30 mJ/cm²) significantly increased the apoptotic rate of Langerhans cells.The apoptotic rate in EGCG group was significantly lower than that in the UVB group,but was higher than that in the control group.Conclusion Rate of apoptosis of Langerhans cells could be increased by UVB irradiation,while EGCG could prevent the increase of apoptosis.

Key words: Langerhans cells, Ultraviolet rays, Epigallocatechin-3-gallate, Apoptosis