| Summary: | 碩士 === 國立中央大學 === 生命科學研究所 === 99 === Natural killer (NK) cells play a pivotal role in the effector arm of host innate immunity defense system. The major functions of NK cells in killing tumor cells or virus-infected host cells were well established. However, whether NK cells can directly kill microbes remains poorly understood. Previous studies have shown that NK cells can use the cytolytic proteins, perforin and granulysin to directly kill the yeast pathogen Cryptococcus neoformans. In this study, using the pathogenic mycobacterium Mycobacterium kansasii which causes a chronic pulmonary infection resembling pulmonary tuberculosis as the study model, I showed that human NK-92 cells directly kill mycobacterium. Killing of M. kansasii by NK92 cells is contact dependent. NK cells use the cytolytic proteins, perforin and granulysin for direct killing, and the underlying killing mechanism is through NKG2D/NCRs, ERK, JNK and p38 MAPK signaling pathways.
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