Mahida Y R, Galvin A, Makh S, Hyde S, Sanfilippo L, Borriello S P, Sewell H F
Divisions of Gastroenterology, University Hospital, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
Infect Immun. 1998 Nov;66(11):5462-9. doi: 10.1128/IAI.66.11.5462-5469.1998.
We have previously shown that Clostridium difficile toxin A induces detachment of human colonic epithelial cells from the basement membrane and subsequent cell death by apoptosis. Because these cells require adhesion-dependent signalling from the extracellular matrix for survival, their detachment from the basement membrane by other means also induces apoptosis. The role of toxin A in the induction of apoptosis therefore remains to be determined. In addition, sensitivities to C. difficile toxin A of lamina propria lymphocytes, macrophages, and eosinophils, which lie below the surface epithelium, are not known. In contrast to epithelial cells, these lamina propria cells do not require adhesion-dependent signalling from the extracellular matrix for survival, and this may allow the mechanisms of toxin A-induced cell death to be further investigated. The aim of this study was to investigate the effect of purified C. difficile toxin A on human colonic lamina propria T cells, macrophages, and eosinophils. We show that C. difficile toxin A induces loss of viability in isolated colonic lamina propria cell preparations containing the three different cell types in a dose- and time-dependent fashion. Exposure to high concentrations of the toxin led to loss of macrophages within 72 h. T-lymphocyte and eosinophil cell death was prominent at later time points and occurred by apoptosis. Exposure to toxin A also induced the production of tumor necrosis factor alpha by the isolated colonic lamina propria cells. However, the presence of neutralizing antibodies to this cytokine did not influence C. difficile toxin A-induced T-cell apoptosis. Moreover, purified T cells also underwent apoptosis following exposure to toxin A, implying that apoptosis occurred as a consequence of a direct interaction between T cells and the toxin. Our studies suggest that C. difficile toxin A is capable of suppressing human colonic mucosal immune responses by inducing early loss of macrophages followed by T-cell apoptosis.
我们之前已经表明，艰难梭菌毒素A可诱导人结肠上皮细胞从基底膜脱离，并随后通过凋亡导致细胞死亡。由于这些细胞需要细胞外基质的黏附依赖性信号来维持生存，它们通过其他方式从基底膜脱离也会诱导凋亡。因此，毒素A在诱导凋亡中的作用仍有待确定。此外，位于表面上皮下方的固有层淋巴细胞、巨噬细胞和嗜酸性粒细胞对艰难梭菌毒素A的敏感性尚不清楚。与上皮细胞不同，这些固有层细胞不需要细胞外基质的黏附依赖性信号来维持生存，这可能有助于进一步研究毒素A诱导细胞死亡的机制。本研究的目的是探讨纯化的艰难梭菌毒素A对人结肠固有层T细胞、巨噬细胞和嗜酸性粒细胞的影响。我们发现，艰难梭菌毒素A以剂量和时间依赖性方式诱导含有这三种不同细胞类型的分离结肠固有层细胞制剂中的细胞活力丧失。暴露于高浓度毒素会导致72小时内巨噬细胞丧失。T淋巴细胞和嗜酸性粒细胞死亡在较晚时间点较为突出，且通过凋亡发生。暴露于毒素A还会诱导分离的结肠固有层细胞产生肿瘤坏死因子α。然而，针对这种细胞因子的中和抗体的存在并不影响艰难梭菌毒素A诱导的T细胞凋亡。此外，纯化的T细胞在暴露于毒素A后也会发生凋亡，这意味着凋亡是T细胞与毒素直接相互作用的结果。我们的研究表明，艰难梭菌毒素A能够通过诱导巨噬细胞早期丧失，随后诱导T细胞凋亡来抑制人结肠黏膜免疫反应。
