Effects of recombinant human interleukin 11 on thrombocytopenia and neutropenia in irradiated rhesus monkeys.

The effects of recombinant human interleukin 11 (rhIL11) on thrombocytopenia and neutropenia in irradiated rhesus monkeys were evaluated after administration different doses at different times. Twenty-three rhesus monkeys were exposed to a total-body irradiation (TBI) with a single dose of 3 Gy 60Co gamma rays. Either placebo, rhIL11 at a dose of 30, 60 or 120 microg/kg day(-1) on days 0-13, or rhIL11 at a dose of 60 microg/kg day(-1) on days 13-26 after TBI was administered to the animals. The results showed that the immediate treatment with rhIL11 but not treatment on days 13-26 resulted in much higher platelet nadirs than in the placebo-treated group. The accelerated recovery of platelets to normal levels after TBI was demonstrated in all groups treated with rhIL11, but the effects of rhIL11 were independent of dose. However, rhIL11 treatment could also accelerate the recovery of leukocytes to normal levels. The numbers of colony-forming bone marrow cells (CFU-E, CFU-Mix, CFU-MK and CFU-GM) in all groups treated with rhIL11 were increased 4- to 14-fold relative to those of the placebo group on day 30. We conclude that rhIL11 may directly promote megakaryocyte development and ameliorate myelosuppression in irradiated monkeys.

Therapeutic Effects of rhIL-11 on Irradiation-Induced Myelosuppression in Rhesus Monkeys.

The efficacy of rhIL-11 in treating thrombocytopenia and neutropenia in gamma-irradiated rhesus monkeys and the variation in curative effect due to difference of administration times were studied. Healthy rhesus monkeys were exposed to 3.0 Gy (60)Co total body irradiation (TBI) to result in pancytopenia for three weeks. Treatment with rhIL-11 (30, 60 or 120 micro g.kg(-1).day(-1)) on early days (days 0 - 13 after TBI) could significantly improve the nadir of platelet count. Although the nadir of leukocyte count was not improved, the duration below 50% of its baseline value was shortened similarly to that of platelet. During the first two weeks after TBI, erythrocyte numbers of the animals treated with these doses of rhIL-11 were lower than those of the control group at first but they became higher beginning from the third week. Four monkeys were treated with rhIL-11 at 60 micro g.kg(-1).day(-1) on days 13 - 26 after TBI. The numbers of their peripheral blood cells followed the similar decrease patterns as those of control group during the first three weeks, then they were improved rapidly. By semi-solid bone marrow cell culture it was demonstrated that rhIL-11 could stimulate bone marrow cells to form more CFU-Meg, CFU-Mix, CFU-E, BFU-E and CFU-GM in vitro. Histopathological observation revealed that bone marrow of the control group was devoid of hematopoietic cells and bleeding, being contrary to that of the group treated with rhIL-11, in which the cells proliferated actively. The results suggest that rhIL-11 can accelerate hematopoietic recovery of irradiated monkeys.