Uptake and intracellular routing of peroxidase-conjugated immunoglobulin-G by the perfused human placenta

Abstract

Selected lobules of term human placenta were extracorporeally perfused and human immunoglobulin-G complexed to horseradish peroxidase (IgG-HRP) was added to the maternal perfusate. After different durations of perfusion IgG-HRP was visualised by use of diamino-benzidine cytochemistry. Within the first 10 min of perfusion IgG-HRP was found bound to microvilli and coated pits of the syncytiotrophoblast; internalisation into coated vesicles and tubulo-vesicular bodies was also observed. Subsequently, IgG-HRP was found in multivesicular bodies and by 30 min appeared in basal vesicles, the frequency of the latter event increasing with time. No routing of IgG-HRP into Golgi regions or lysosomes could be detected. by 60 min IgG-HRP was found in a few caveolae of fetal endothelium of both terminal and intermediate villi. IgG-HRP was not found in intercellular clefts of the endothelium. The pattern of uptake and routing observed suggests a receptor-mediated transcytosis of IgG-HRP across the syncytiotrophoblast and a transcellular pathway through the endothelium.

Receptor-mediated uptake and transport of macromolecules in the human placenta

“…Electron microscopy had been used to trace the pathway of horseradish peroxidase conjugate of IgG through the different tissue layers of the human placenta (Leach et al, 1990). The delay of 2 hours between the start of perfusion of the intervillous space with the conjugated IgG and its detection in endothelial cells of the villous capillaries was consistent with the lag time after addition of IgG to the maternal perfusate until it was detected on the fetal side as observed in the study of Malek et al (1995).…”

Effects of endocytosis inhibitors on internalization of human IgG by Caco-2 human intestinal epithelial cells

“…The reason for the inconsistencies between these results is not clear at present, but it might be due to the differences in experimental conditions including the culture cells employed. Earlier electron microscopic studies revealed that IgG was observed in coated pits and coated vesicles in the new born rat intestine and the syncytiotrophoblast of human term placenta (Abrahamson and Rodewald 1981;Leach et al 1990). In addition, recently, He et al (2008) showed that a coated vesicle pinching off from a coated pit was involved in the first steps of FcRn-mediated IgG transport in neonatal rat intestine.…”

Role of maternally derived immunity in fish

“…In mammals, IgG transfer is achieved through an active transport mechanism, involving a receptor mediated transcytosis of IgG across the syncytiotrophoblast, and a transcellular pathway through the endothelium [148,149]. In teleosts, although the transfer and the mechanism of uptake, transport and proteolysis of different specific serum proteins to eggs during vitellogenesis are already known [149][150][151][152][153][154], the mechanism of IgM uptake and its storage within the eggs is yet to be established.…”