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From the M. D. Anderson Hospital and Tumor Institute at Houston, The Departments of Biochemistry and Virology, and the Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas 77025
Abstract
Studies are described which establish the glycocalyx as the morphologic site for the binding of IgG to the membrane of the rabbit yolk sac and which indicate that micropinocytotic vesiculation is the mechanism for its cellular uptake.
Yolk sac membranes were exposed in vivo and in vitro to rabbit antihorse ferritin antibody. The membranes were then treated with ferritin and examined by electron microscopy for deposition of ferritin. Deposits of IgG-bound ferritin were found localized at the glycocalyx coat of the microvilli, intermicrovillar pits, and incipient micropinocytotic vesicles.
Stages in the micropinocytotic process are shown, depicting internalization of microvillial membrane surfaces, indicating that this is the mechanism by which IgG is taken up by the fetal yolk sac from the maternal uterine lumen for transfer to the fetus.
These findings are discussed in the context of the specificity and kinetic characteristics of the transfer process.
Footnotes
1 This investigation was supported in part by National Science Foundation Grant GB 13650.
2 Present address: Osaka Prefectural Institute of Public Health, Osaka, Japan.
3 Present address: Hamanomachi Hospital, Fukuoka, Japan.
4 To whom requests for reprints should be addressed.
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