Protein selection in the yolk-sac splanchnopleur of the rabbit: the fate of globulin injected into the foetal circulation

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Abstract
Globulins originating in another species are treated in the circulation of the rabbit in the same way as is homologous globulin. Twenty-four hours after intravenous injection of mixed antitoxin preparations the relative concentrations of rabbit and bovine antitoxins in the foetal sera are unchanged. There is no evidence of differential treatment of homologous and heterologous protein after entry to the foetal circulation. Since serum globulins taken up from the uterine cavity of the rabbit by the yolk-sac splanchnopleur reach differential concentrations in the foetal serum depending upon the species of origin of the globulin, selection must occur during passage of the protein through the tissues of the yolk-sac splanchnopleur itself. The rate of removal of globulin from the foetal circulation during the first 24 hours is not more rapid than in the adult. No evidence could be found of any passage of intact globulin across the placenta from the foetal to the maternal circulation.