Permeability studies on taenid metacestodes: I. Uptake of proteins by larval stages of Taenia taeniaeformis, T. crassiceps, and Echinococcus granulosus.

Host immunoglobulins of several different classes were detected within the bladder fluids of Taenia taeniaeformis, T. crassiceps, and Echinococcus granulosus. Radioiodinated proteins were taken up in vitro by larvae of both T. taeniaeformis and T. crassiceps and were shown to retain their physicochemical and antigenic characteristics. Rates of uptake were similar in the 2 species and were not related to the molecular weight of the proteins. Immunoglobulins were taken up both in vitro and in vivo by larvae of T. taeniaeformis. Absorbed immunoglobulins were shown to retain both antigen binding capacity and biologic functions associated with the Fc portion of the molecules. Not all cysts of E. granulosus contained detectable host proteins. Uptake of 125I occurred when hydatid cysts were exposed to labeled proteins in vitro, but it appeared that rapid degradation of the labeled carrier led to the appearance of dialysable fragments. This may be attributable to proteolysis within the bladder fluid. We conclude that taeniid metacestodes are capable of absorbing a variety of proteins, and that these macromolecules can retain their structural and functional integrity following transport. This absorptive capacity accounts for the presence of host serum components within bladder fluids.