大蜡螟（Galleria mellonella）的血细胞-血细胞黏附及结瘤反应受霍乱毒素及其B亚基的影响。
Hemocyte-hemocyte adhesion and nodulation reactions of the greater wax moth, Galleria mellonella are influenced by cholera toxin and its B-subunit.
作者信息
Lapointe Jason F, Dunphy Gary B, Mandato Craig A
机构信息
Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, Quebec, Canada H3A 2B2.
Department of Natural Resource Sciences, Macdonald Campus of McGill University, 21, 111 Lakeshore Road, Ste. Anne de Bellevue, Québec, Canada H9X 3V9.
出版信息
Results Immunol. 2012 Feb 25;2:54-65. doi: 10.1016/j.rinim.2012.02.002. eCollection 2012.
Nodulation, the lepidopteran insect immune response to large numbers of microbes in the blood (hemolymph) consists of the coordination of the blood cell (hemocyte) types the granular cells and plasmatocytes in terms of granular cell-bacteria adhesion and hemocyte-hemocyte adhesion (microaggregation). Hemocyte-microbe adhesion is influenced by the secondary messenger, cAMP, and cAMP-dependent protein kinase A. In the present study, cholera toxin, an AB5 protein known to indirectly stimulate adenylate cyclase, is used to examine the hemocyte responses to glass, bacteria and hemocyte-hemocyte microaggregates. In vitro, this toxin induces a bimodal hemocyte adhesion response that varies with the holotoxin concentration in terms of the individual and aggregated hemocyte adhesion responses: the lower CTX concentration (1.2 nM) increases microaggregate adhesion and decreases individual hemocyte binding to glass, as does higher concentrations (6-120 nM), however microaggregates induced by lower concentrations do not adhere to glass. Cholera toxin-induced microaggregation is inhibited by RGDS, suggestive of integrin involvement. In vivo, cholera toxin (1.2-120 nM) injected into larvae induces also a bimodal hemocytic response: low levels (1.2-6 nM) cause reduced hemocyte adhesion, while high levels (12-120 nM) increase hemocyte release or mobilization of adhesive hemocyte counts in the hemolymph. Increasing levels of cholera toxin concomitantly injected with the non-pathogenic bacterium, Bacillus subtilis produces a bimodal pattern in bacterial removal from the hemolymph which correlates with nodule frequency in larvae injected with cholera toxin only. The effects of higher concentrations of cholera toxin in vitro (6-120 nM) and in vivo (12-120 nM) are mediated by the B-subunit, whereas the isolated A-subunit has no effect on hemocyte activity. Cholera toxin and its individual subunits did not detectably alter levels of intracellular cAMP in the hemocytes, suggesting a cAMP-independent mechanism stimulating the nodulation response.
结瘤反应是鳞翅目昆虫对血液（血淋巴）中大量微生物的免疫反应，它包括血细胞（血球）类型（颗粒细胞和浆细胞）在颗粒细胞与细菌黏附以及血球与血球黏附（微聚集）方面的协调。血球与微生物的黏附受第二信使环磷酸腺苷（cAMP）和cAMP依赖性蛋白激酶A的影响。在本研究中，霍乱毒素（一种已知可间接刺激腺苷酸环化酶的AB5蛋白）被用于检测血球对玻璃、细菌和血球与血球微聚集体的反应。在体外，这种毒素诱导出一种双峰血球黏附反应，其在个体和聚集血球黏附反应方面随全毒素浓度而变化：较低的霍乱毒素浓度（1.2 nM）会增加微聚集体黏附，并减少单个血球与玻璃的结合，较高浓度（6 - 120 nM）时也是如此，然而较低浓度诱导的微聚集体并不黏附于玻璃。霍乱毒素诱导的微聚集被RGDS抑制，这表明整合素参与其中。在体内，注射到幼虫体内的霍乱毒素（1.2 - 120 nM）也诱导出一种双峰血球反应：低水平（1.2 - 6 nM）导致血球黏附减少，而高水平（12 - 120 nM）则增加血球释放或血淋巴中黏附性血球计数的动员。与非致病性细菌枯草芽孢杆菌同时注射的霍乱毒素水平升高，会在从血淋巴中清除细菌时产生一种双峰模式，这与仅注射霍乱毒素的幼虫中的结节频率相关。体外较高浓度（6 - 120 nM）和体内（12 - 120 nM）的霍乱毒素的作用是由B亚基介导的，而分离出的A亚基对血球活性没有影响。霍乱毒素及其单个亚基并未显著改变血球内的cAMP水平，这表明存在一种不依赖cAMP的机制来刺激结瘤反应。
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