Selective and Directional Transfer of 7S γ₂-Globulin across the Human Placenta

Abstract

RABBIT γ₂-globulin can be hydrolysed by papain into three polypeptide fragments which are nearly equal in size: two of these fragments, I and II, each possess an active antibody site, whereas the third fragment, III, has no antibody activity¹. Brambell et al. examined the maternofœtal transfer of such fragments in the pregnant rabbit, and reported that the amount of fragment III to be found in the fœtus after administration to the mother was 6–10 times the amount of fragments I or II and only a fourth the amount of the parent γ₂-globulin². It was concluded that the fragments pass from mother to fœtus less readily than does the intact γ₂-globulin molecule, and that the transmissibility of γ₂-globulin from doe to fœtus is attributable to that part of the molecular structure represented by the non-antibody fragment. In the study reported here, this concept was reinvestigated as to its applicability to the metabolism of 7S γ₂-globulin in man.