Abstract: AIM :To evaluate the radioprotective ef- fects and cytoprotective activities of the facteur thymic se- rique ( FTS) to reduce certain side-effects in the chemo- therapy in mice .METHODS:Except of control group, all mice which received acute whole-body Co-60-gamma irradiation were randomized to 5 groups :Saline solution was given to model group, 0 .025, 0 .25, and 2 .5 mg·kg ^-1·day ^-1 for 7 consecutive days FTS to low or me- dial or large dose of FTS group by s .c., 2 .5 mg·kg ^-1 nilestriol to control drug group by i .g .at 1st day and the radioprotective efficacy of FTS was determined by immuni- ty effects and by measuring 30-day survival at 6 .0 Gy or 7 .0 Gy .The same doses above of FTS were investigated by measuring 20-day survival at 100 mg·kg ^-1 d-1 for 14 consecutive days cyclophosphamide injury in mice with H22 liver cancer cell for its cytoprotective activities to re- duce certain side-effects in the chemotherapy of cancer. RESULTS :The leucocyte total number, phagocyte com- petence and thymus index were enhanced significantly when compared with the model group ( P <0 .05) , but spleen index increased than those of nilestriol group ( P > 0 .05) .Thirty-day survival for 0 .25 mg·kg ^-1 FST ad- ministered mice at 7 .0 Gy was significantly increased in comparison with saline administered mice ( P <0 .05) and the survival days were longer ( P <0 .01) , the same as nilestriol group .20-day survival was increased for FST to inhibit cyclophosphamide-induced injury in mice with tumors .CONCLUSIONS:FTS developed in our labora- tory provides significant protection from acute whole-body gamma irradiation or chemotherapy ( cyclophosphamide) injury in mice .It may play an important role in the mani- festation of its radioprotective and cytoprotective efficacy .

Key words: facteur thymic serique ;radioprotective , immunostimulatory effects ;mice with tumors ;side-effects in the chemotherapy ;survival rate