Chávez B, Knaippe F, Gonzalez-Mariscal L, Martínez-Palomo A
Exp Parasitol. 1986 Jun;61(3):379-89. doi: 10.1016/0014-4894(86)90194-3.
The pathogenicity of Giardia lamblia is a subject of debate. Some studies of human biopsy material have mentioned the presence of trophozoites inside the intestinal mucosa, while in others, flagellates have only been found attached to the epithelium. To study the possible cytopathic effects of G. lamblia cultured under axenic conditions, trophozoites of the human 1/Portland and WB strains were placed in contact with monolayers of Madin Derby Canine Kidney cells, a well characterized cell strain with morphological and functional properties similar to those of a transporting epithelium. After 24 and 48 hr of interaction, the effect of the parasite on epithelial cells was assessed by transmission, scanning, and freeze fracture electron microscopy. In addition, the possible action of living trophozoites and sonicates of G. lamblia on the transepithelial resistance of MDCK monolayers mounted in Ussing chambers was analyzed for periods varying up to 48 hr. The results demonstrate that G. lamblia trophozoites do not invade epithelial monolayers. Furthermore, the parasites fail to produce cytoplasmic changes on target cells and have no effect on transepithelial resistance as judged both electrophysiologically and by the failure to open the occluding junctions that bind together epithelial cells. Damage induced by the parasites to cultured cells was limited to focal distortion or depletion of microvilli at the site of adhesion, which may progress to leave circular areas devoid of microvilli, different from the adhesion marks reported by others for G. muris. Therefore, under the in vitro conditions described here, giardias showed no toxic or invasive effect.
蓝氏贾第鞭毛虫的致病性是一个有争议的话题。一些对人体活检材料的研究提到在肠黏膜内存在滋养体，而在其他研究中，仅发现鞭毛虫附着于上皮细胞。为了研究在无菌条件下培养的蓝氏贾第鞭毛虫可能的细胞病变效应，将人1/波特兰株和WB株的滋养体与麦迪逊-达比犬肾细胞单层接触，该细胞株具有良好的特征，其形态和功能特性与转运上皮细胞相似。在相互作用24小时和48小时后，通过透射电子显微镜、扫描电子显微镜和冷冻断裂电子显微镜评估寄生虫对上皮细胞的影响。此外，分析了活的蓝氏贾第鞭毛虫滋养体及其超声裂解物对安装在尤斯灌流小室中的MDCK单层细胞跨上皮电阻的可能作用，观察时间长达48小时。结果表明，蓝氏贾第鞭毛虫滋养体不侵入上皮单层细胞。此外，寄生虫未能在靶细胞上产生细胞质变化，并且在电生理判断以及未能打开连接上皮细胞的紧密连接方面，对跨上皮电阻均无影响。寄生虫对培养细胞造成的损伤仅限于黏附部位微绒毛的局灶性扭曲或缺失，这种情况可能会发展为留下没有微绒毛的圆形区域，这与其他文献报道的鼠贾第虫的黏附标记不同。因此，在此处描述的体外条件下，贾第虫未显示出毒性或侵袭作用。
