[Effects of Klebsiella pneumoniae on the expression of cytokines by polymorphonuclear neutrophil granulocytes in mice].

OBJECTIVE:To observe the effect of Klebsiella pneumoniae (Kle.p) on the expression of cytokines in mouse polymorphonuclear neutrophil granulocytes (PMNs). METHODS:Mouse models of acute pneumonia were induced by intranasal inoculation of 30 microl PBS containing 1 x 10(7) Kle.p (heat-inactivated at 60 degrees C for 1.5 h). The mRNA and protein expressions of the cytokines in the isolated and purified PMNs were assayed by reverse transcriptional (RT)-PCR, Western blotting and enzyme- linked immunosorbent assay (ELISA), respectively. RESULTS:Kle.p infection induced the mRNA expressions of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta in the early stage, and TNF-alpha mRNA reached its peak at 6 h and IL-1beta mRNA at 12 h after infection, both of which decreased 24 h after infection. Western blot analysis showed that the protein expressions of TNF-alpha and IL-1beta were the highest at 6 h, and decreased obviously at 24 h after infection. ELISA showed that the secretion of TNF-alpha peaked at 6 h and decreased obviously at 24 h after infection, while the peak of IL-1beta production occurred at 12 h and maintained the high level till 24 h after the infection. CONCLUSION:TNF-alpha may participate in the immune defense of PMN against Kle.p infection mainly in the early stage of infection while IL-1beta mainly in the later stage.