Preparation and developmental toxicity of monoclonal antibodies against rat visceral yolk sac antigens

Thirty clones producing monoclonal antibodies (MCAs) to rat visceral yolk sac (VYS) antigens have been prepared. These MCAs localized by immunofluorescence in the VYS endoderm in vitro and were tested for developmental toxicity by intraperitioneal injection of ascites fluid into pregnant rats on day 9 of gestation. Five of the hybridomas produced MCAs that induced embryonic death, malformation, and growth retardation; the other MCAs had no developmental toxicity. Five MCAs, three teratogenic and two nonteratogenic, were tested for their ability to inhibit pinocytosis in the isolated day 17-VYS. Only the teratogenic MCAs were inhibitory, providing further evidence for the hypothesis that teratogenic antibodies interfere with the nutritional supply to the embryo.