Stirpe F, Derenzini M, Barbieri L, Farabegoli F, Brown A N, Knowles P P, Thorpe P E
Dipartimento di Patologia sperimentale dell'Università di Bologna, Italy.
Virchows Arch B Cell Pathol Incl Mol Pathol. 1987;53(5):259-71. doi: 10.1007/BF02890252.
Immunotoxins were prepared by conjugating saporin, a ribosome-inactivating protein from Saponaria officinalis, to a monoclonal antibody against the Thy1.1 antigen, or to its F(ab')2 fragment. The immunotoxins were eight- to 16-fold more toxic to mice than free saporin. Injection of the immunotoxins induced necrosis of the liver and spleen, whereas free saporin caused necrosis of the epithelium of the kidney tubules. The cytoplasm of the hepatic parenchymal cells was affected by the immunotoxins, lesions being apparent in the rough endoplasmic reticulum and, later, in the mitochondria. These changes were associated with a reduced capacity to synthesise proteins both in the intact liver and by isolated liver microsomes. Studies of the in vivo distribution showed that 90% of the free saporin was removed from the bloodstream, mainly by the kidneys, within 10 min of injection. By contrast, the immunotoxins persisted in the blood for several hours and the only organ in which they consistently accumulated was the liver. The hepatotoxic effect of the immunotoxins was not due to their binding to liver cells via the antigen-binding sites or the Fc-piece of the antibody moiety, nor was it due to hepatic recognition of carbohydrate in the immunotoxin. It is concluded that free saporin, although capable of entering liver cells, is filtered so rapidly by the kidney that liver damage does not occur to a significant extent. Filtered saporin, however, is reabsorbed by renal tubules, whose epithelial cells are damaged. The antibody-saporin conjugate is too large to filter at the glomerulus and so has greater opportunity to penetrate into and to damage the hepatic parenchymal cell.
免疫毒素是通过将肥皂草素（一种来自肥皂草的核糖体失活蛋白）与抗Thy1.1抗原的单克隆抗体或其F(ab')2片段偶联而制备的。这些免疫毒素对小鼠的毒性比游离肥皂草素高8至16倍。注射免疫毒素会导致肝脏和脾脏坏死，而游离肥皂草素会导致肾小管上皮细胞坏死。肝实质细胞的细胞质受到免疫毒素的影响，粗面内质网出现明显病变，随后线粒体也出现病变。这些变化与完整肝脏以及分离的肝微粒体中蛋白质合成能力的降低有关。体内分布研究表明，注射后10分钟内，90%的游离肥皂草素从血液中清除，主要通过肾脏。相比之下，免疫毒素在血液中持续存在数小时，它们持续积累的唯一器官是肝脏。免疫毒素的肝毒性作用并非由于它们通过抗体部分的抗原结合位点或Fc片段与肝细胞结合，也不是由于肝脏对免疫毒素中碳水化合物成分的识别。得出的结论是，游离肥皂草素虽然能够进入肝细胞，但被肾脏过滤得非常快，以至于肝脏不会受到显著损伤。然而，被过滤的肥皂草素会被肾小管重吸收，而肾小管上皮细胞会受到损伤。抗体 - 肥皂草素偶联物太大，无法在肾小球处过滤，因此有更多机会渗透并损伤肝实质细胞。
