CCL20抑制小鼠胸腺CD4^＋CD25^＋天然调节性T细胞的发育

本研究探讨趋化因子CCL20对小鼠胸腺CD4^＋CD25^＋双阳性调节性T细胞发育的影响,为天然调节性T细胞调控的研究提供基础数据。采用14.5天龄胚鼠胸腺进行体外培养,以FACS检测不同时间点胸腺CD4^＋CD25^＋细胞的改变,同时计数每个胸腺小叶的细胞数变化。结果表明：体外胸腺培养的第1-6天胸腺细胞比例、细胞数量的变化趋势与胸腺体内发育的第14.5、15、16、17、18、19天CD4^＋CD25^＋双阳性T细胞的比例、细胞数量的变化趋势相似;在胸腺体外培养的第1-6天,CD4＋CD25^＋T细胞占CD4^＋T细胞的比例分别为58.29%、12.14%、6.08%、17.78%、9.06%、4.04%,占CD25^＋T细胞的比例分别为3.75%、10.81%、17.20%、51.93%、61.64%、80.06%,这一发育趋势与体内结果具有一致性。在4μg/ml的CCL20干预下,胸腺体外培养的第3、6天CD4^＋CD25^＋胸腺细胞分别从3.24±0.18、3.96±0.24下降至1.27±0.11、1.76±0.22（p值均〈0.001）。结论：体外培养的CD4^＋CD25^＋双阳性胸腺细胞数量和比例变化与体内发育变化趋势一致,CCL20明显下调胸腺CD4^＋CD25^＋的表达,这将为天然调节性T细胞的调控研究提供有效的参考依据。

Inhibitory Effect of CCL20 on CD4+CD25+Regulatory T Cell Development in Mouse Thymus

The aim of this study was to investigate the roles of chemokine CCL20 in development of CD4(+)CD25(+) thymocytes by means of fetal thymus organ culture. Fetal mouse thymus lobes were removed at the fetus age of 14.5 days and cultured in complete RPMI 1640 with 20% FBS in vitro. Phenotypes of the thymocytes were analyzed by FACS and the number of cells per lobe was counted. The results revealed that from day 14.5 to day 19, the absolute and relative numbers of the CD4(+)CD25(+) thymocytes varied similarly as their development as in vitro culture at 6 days. Data showed that during the 6 days in vitro culture the CD4(+)CD25(+) cell percentage out of CD4(+) cells was 58.29%, 12.14%, 6.08%, 17.78%, 9.06%, 4.04% and the CD4(+)CD25(+) cell percentage out of CD25(+) cells was 3.75%, 10.81%, 17.20%, 51.93%, 61.64%, 80.06%. All these data indicated similar characters to their development in vivo. Moreover, at interference with CCL20, the percentage of CD4(+)CD25(+) T cells in thymocytes significantly decreased at the 3 and 6 days from 3.24+/-0.18 and 3.96+/-0.24 to 1.27+/-0.11 (p<0.001) and 1.76+/-0.22 (p<0.001) respectively. It is concluded that the development of CD4(+)CD25(+) thymocytes is similar both in vitro and in vivo, interfering with CCL20 significantly downregulate the expression of CD4(+)CD25(+) T cells. The above data may help to understand the development of naturally arising CD4(+)CD25(+) regulatory T cells.