Abstract: 【Abstract】 Objective To evaluate the effect of epigallocatechin gallate （EGCG） on T helper cell 1 （Th1） and Th2 in psoriasis patients. Methods A total of 33 patients with plaque?type psoriasis vulgaris were enrolled, and peripheral blood mononuclear cells （PBMC） were isolated and cultured. The appropriate concentration of EGCG was determined by methyl thiazol tetrazolium （MTT） assay. PBMC at exponential growth phase were divided into 2 groups to be treated with EGCG （EGCG group） or not （control group） for 24 hours. Flow cytometry was performed to determine proportions of Th1 and Th2 cells, enzyme?linked immunosorbent assay （ELISA） to detect levels of Th1 （interleukin ［IL］?2, interferon ［IFN］?γ） and Th2 cytokines （IL?4, IL?10） in the cell culture supernatant, and real?time quantitative RCR （qRT?PCR） to determine the mRNA expression of T?bet （a Th1 transcription factor） and GATA3 （a Th2 transcription factor）. Statistical analysis was carried out by using t test. Results According to the MTT assay results, EGCG at a non?toxic concentration of 60 μmol/L was chosen for subsequent experiments. Compared with the control group, the EGCG group showed significantly decreased number of Th1 cells （t = 3.43, P = 0.026）, increased number of Th2 cells （t = 6.68, P = 0.026）, and decreased Th1/Th2 ratio （P < 0.05）. The levels of IL?2 and IFN?γ in the culture supernatant of PBMC were both significantly lower in the EGCG group （824.45 ± 101.21 ng/L, 1 623.62 ± 185.56 ng/L respectively） than in the control group （1 568.32 ± 196.45 ng/L, 3 287.63 ± 235.54 ng/L respectively）, while the levels of IL?4 and IL?10 were significantly higher in the EGCG group （389.48 ± 46.63 ng/L, 285.95 ± 53.28 ng/L respectively） than in the control group （225.38 ± 26.92 ng/L, 165.46 ± 32.25 ng/L respectively）. Compared with the control group, the EGCG group showed significantly decreased T?bet mRNA expression （t = 11.99, P < 0.001）, but increased GATA3 mRNA expression （t = 18.62, P < 0.001）. Conclusion EGCG can reduce the number of Th1 cells, inhibit the production of Th1 cytokines and transcription factors, and increase the number of Th2 cells and the production of Th2 cytokines and transcription factors, followed by the modulation of Th1/Th2 immune imbalance.

Key words: Psoriasis, Th1 cells, Th2 cells, Interferon-gamma, Interleukins, Transcription factor, Epigallocatechin gallate