Abstract: AimTo determine the protective effect of recombinant human interleukin-2 (rhIL-2) in inhalant form on experimental respiratory tract infection with Klebsiella pneumoniae in mice. Methods Mice were infected with the method of nasal intubation drip. During infection, mice were given rhIL-2 by sc injection and the method of nasal intubation drip. There were normal group, vehicle group, model group, rhIL-2 groups and gentamicin group. In the end, the pathological changes in the lung were observed. The survival time and the mortality within a week of each group were recorded. The total protein content, the albumin content, the activity of alkaline phosphatase and the activity of lactic dehydrogenase of broncho-alveolar lavage fluid (BALF) were dertermined and compared. ResultsSymptoms of Klebsiella pneumoniae were remarkably relieved because of rhIL-2 administration. The total protein content, the albumin content, the activity of alkaline phosphatase and the activity of lactic dehydrogenase of BALF were less than those in the vehicle group and the model group. ConclusionInhalation of rhIL-2 can alleviate the pathological changes in the lung after infection. At the same dose, it could be seen that the effect of rhIL-2 in inhalant form was better than that of the injection.