Summary
High doses of rHIL-1 protected C3H/HeN mice against lethal radiation damage. The optimum time of radioprotection was found when this cytokine was administered at 4 h and at 20 h before irradiation. The dose reduction factors when the IL-1 was administered at those times were about 1·30. The radioprotection at the optimum times was also observed in the cell kinetic behaviour of GM-CFC in the bone marrow. In previous studies it was reported that less radioprotection was found in C3H/HeN mice pretreated with IL-1. This may not be the case with a higher dose of IL-1.