Objective To explore the impact and possible mechanism of Qingfei Yishen Fang （清肺益肾方）combined with levofloxacin tablet on immune function of aged rats’ infected by Klebsiella pneumonia.Methods Sixty rats were randomized into the blank group

the model group

the levofloxacin group

the combination of high

median and low dose group

10 rats in each group.Rats in other groups were made models of aged rats infected by Klebsiella pneumonia by disposable tracheal intubation method of dropping bacteria except the blank group.On the 2 nd day of successful modeling

the blank group and the model group were given normal saline 10 g/ （kg · d） by gavage.The combination of high

median and low dose groups were given Qingfei Yishen Fang extract 30.66

15.33

7.67 g/ （kg·d） by gavage respectively; meanwhile

each group was given levofloxacin tablet suspension 42mg/ （kg·d） by gavage.The levofloxacin group was given evofloxacin tablet suspension 42 mg/ （kg·d） by gavage.After administration for 6 days

it was examined in each group that rats’ general condition

pathological changes of lung tissue

the expressions of serum immunoglobulin G （IgG） and immunoglobulin A （IgA）

as well as the changes of IgG

IgA and secretory immunoglobulin A （s IgA） in broncho-alveolar lavage fluid.Results Lung tissue pathology showed that rat lung injury in the model group was heavier than that in the blank group.Rat lung injury in the treating groups got varying degrees of relief compared with the model group.Compared with the blank group

serum IgG

IgA and broncho-alveolar lavage fluid IgA in the model group increased; while the expressions of broncho-alveolar lavage fluid IgG and s IgA decreased （P < 0.01）.Compared with the model group

the expressions of serum IgG

IgA and broncho-alveolar lavage fluid IgA in the levofloxacin group

the combination of high

median and low dose groups decreased.The expressions of broncho-alveolar lavage fluid IgG and s IgA increased in the combination of high and median dose groups （P < 0.05 or P < 0.01）.Serum IgG in the combination of median dose group was lower than that in the combination of high and low dose groups.Serum IgG in the combination groups was lower than that in the levofloxacin group （P < 0.01）.The expression of broncho-alveolar lavage fluid s IgA in the combination of high and median dose groups was higher than that in the levofloxacin group （P < 0.01）.Conclusion Qingfei Yishen Fang combined with levofloxacin tablet might improve the aged rats’ lung tissue injury infected by Klebsiella pneumonia.The mechanism might relate to reducing peripheral blood inflammatory response and improving the local immunity of lung.