Uptake and transport of immunoglobulin by the chick choroid plexus

Summary The choroid plexus from the lateral ventricles of 18-day chick embryos was cultivated as an organ in medium 199 until the degeneration of the stroma. Selected plexuses forming an empty epithelial sac were then incubated with enzyme-treated human immunoglobulin (5S-antibody) and with native human immunoglobulin (7S-antibody). Uptake of the 7S-antibody was observed after 30 min, whereas the 5S-antibody was taken up by the choroid plexus within 1 min, as demonstrated by means of the peroxidase-anti-peroxidase (PAP) technique (Sternberger 1974). The antibodies were located in conspicuous, large vacuoles of the choroid epithelium. Further experiments were performed using only 5S-antibody. In addition to the demonstration of the protein structure of this immunoglobulin, it was also shown that its binding capacity for tetanus toxoid as an antigen remains intact in the intracellular location. It was not possible to observe lysosomal degradation. Moreover, 5S-antibody was detectable in cultures first incubated with 5S-antibody for 30 min and subsequently in antibody-free medium for a further period of 7 to 11 days.The biological significance of the uptake of material from the cerebrospinal fluid and the possibility of the existence of a receptor for 5S-antibody are discussed.