Effect Of Infection From Klebsiella On The Production Of Cytokines And Apoptosis Of The Thymocytes In Mice

OBJECTIVE: To investigate the productive kinetics of cytokines during the infection of negative-gram bacteria and the relation of the infection and apoptosis in the thymus, and to observe the variation of the serum cytokine levels and the effect on immune function when infected in order to explain the role of cytokines in severe infection, damage of organ, as well as the thymocyte apoptosis.METHOD: Sepsis model of NIH mice was established successfully by intraperitoneal injection of suspension of Klebsiella isolated from clinical practice. Serum levels of TNF-α,IL-1β,IL-6 were determined by mice ELISA Kits 3, 6, 9, 12, 24 hours after infection, respectively. Apoptosis of thymocytes after bacterial infection and apoptosis in the thymus after i.p injection of cefodizime and amikacin were detected with Flow cytometric assessment. The morphologic changes of thymocyte apoptosis were observed by electron microscope 9 hours after infection.RESULTS: The serum level of IL-1β resched its peak 3 hours afterinfection, then declined to fail to be detected 24 hours after infection. The serum level of IL-6 reached high concentration 6 hours after infection, then decreased rapidly, IL-6 could still be detected 24 hours after infection. TNF-αincreased slowly and reached high concentration 9 hours after infecton, then dropped rapidly and maintained a comparatively low level in the serum. The rate of apoptosis in the thymus increased continuously 3 hours after infection and reached its peak 24 hours after infection. There existed significant difference (p<0.05) between the controls and the infections at the same time points. However, it was shown that the thymocyte apoptosis decreased significantly after injection of cefodizime or amikacin (p<0.05), compared with the controls. The typical morphologic changes of apoptosis in the thymus after infection were manifested by means of electron microscope. CONCLUSION: The inflammatory cytokines can be released and the apoptosis of thymocytes are caused by negative-gram bacterial infection. The application of cefodizime and amikacin can significantly inhibit the thymocyte apoptosis and strengthen the immune systerm against infection.