Marr Kaleb J, Jones Gareth J, Zheng Chunfu, Huston Shaunna M, Timm-McCann Martina, Islam Anowara, Berenger Byron M, Ma Ling Ling, Wiseman Jeremy C D, Mody Christopher H
Department of Medical Science, University of Calgary, Calgary, Alberta, Canada.
Infect Immun. 2009 Jun;77(6):2436-46. doi: 10.1128/IAI.01232-08. Epub 2009 Mar 23.
NK cells, in addition to possessing antitumor and antiviral activity, exhibit perforin-dependent microbicidal activity against the opportunistic pathogen Cryptococcus neoformans. However, the factors controlling this response, particularly whether the pathogen itself provides an activation or rearming signal, are largely unknown. The current studies were performed to determine whether exposure to this fungus alters subsequent NK cell anticryptococcal activity. NK cells lost perforin and mobilized lysosome-associated membrane protein 1 to the cell surface following incubation with the fungus, indicating that degranulation had occurred. Despite a reduced perforin content during killing, NK cells acquired an enhanced ability to kill C. neoformans, as demonstrated using auxotrophs that allowed independent assessment of the killing of two strains. De novo protein synthesis was required for optimal killing; however, there was no evidence that a soluble factor contributed to the enhanced anticryptococcal activity. Exposure of NK cells to C. neoformans caused the cells to rearm, as demonstrated by increased perforin mRNA levels and enhanced loss of perforin when transcription was blocked. Degranulation alone was insufficient to provide the activation signal as NK cells lost anticryptococcal activity following treatment with strontium chloride. However, NK cells regained the activity upon prolonged exposure to C. neoformans, which is consistent with activation by the microbe. The enhanced cytotoxicity did not extend to tumor killing since NK cells exposed to C. neoformans failed to kill NK-sensitive tumor targets (K562 cells). These studies demonstrate that there is contact-mediated microbe-specific rearming and activation of microbicidal activity that are necessary for optimal killing of C. neoformans.
自然杀伤细胞（NK细胞）除了具有抗肿瘤和抗病毒活性外，还表现出对机会性病原体新型隐球菌的穿孔素依赖性杀菌活性。然而，控制这种反应的因素，特别是病原体本身是否提供激活或重新武装信号，在很大程度上尚不清楚。进行当前研究以确定接触这种真菌是否会改变随后NK细胞的抗隐球菌活性。与真菌孵育后，NK细胞失去穿孔素并将溶酶体相关膜蛋白1转运至细胞表面，表明发生了脱颗粒。尽管在杀伤过程中穿孔素含量降低，但如使用营养缺陷型菌株独立评估对两种菌株的杀伤所证明的，NK细胞获得了增强的杀伤新型隐球菌的能力。最佳杀伤需要从头合成蛋白质；然而，没有证据表明可溶性因子有助于增强抗隐球菌活性。如穿孔素mRNA水平升高以及转录受阻时穿孔素损失增加所证明的，NK细胞暴露于新型隐球菌会导致细胞重新武装。单独的脱颗粒不足以提供激活信号，因为用氯化锶处理后NK细胞失去了抗隐球菌活性。然而，长时间暴露于新型隐球菌后NK细胞恢复了活性，这与微生物激活一致。增强的细胞毒性并未扩展到肿瘤杀伤作用，因为暴露于新型隐球菌的NK细胞未能杀伤对NK敏感的肿瘤靶标（K562细胞）。这些研究表明，存在接触介导的微生物特异性重新武装和杀菌活性激活，这对于最佳杀伤新型隐球菌至关重要。
