Teratogenic antibody internalization by rat visceral yolk-sac endoderm in vitro: an ultrastructural colloidal gold tracer study

Multiple antigens in the rat visceral yolk sac induce teratogenic antisera

Preparative isoelectric focusing was used to fractionate the supernatant from a homogenate of day 19 rat visceral yolk sac. Three fractions, of pI ranges 3.5-5.0, 5.0-7.0, and 7.0-9.0, were isolated and used to immunize rabbits, by four or six weekly injections, each containing 5 mg protein. The resulting antisera were all teratogenic when injected into rats on day 9 of gestation, but widely differing potencies were observed. The most potent antiserum was that against yolk sac components focusing in the pI 7.0-9.0 range: An optimum teratogenic dose of 50 mg protein per kg body weight was observed, and a dose of 100 mg/kg was shown to cause 100% embryonic resorption. Antiserum against the fraction focusing in the pI 3.5-5.0 range was the least teratogenic: A significant incidence of embryonic malformation and death was seen only at doses of 600 mg/kg and above. The two fractions that yielded the more teratogenic antisera were refocused over narrower pH ranges, yielding four subfractions in the pI 5.0-7.0 range and eight subfractions in the pI 7.0-9.0 range. Antisera against each of these 12 fractions were raised in rabbits; most of these antisera were shown to be teratogenic, although of differing potencies. It is concluded that the yolk sac contains many antigens that can elicit antibodies with teratogenic and yolk sac-localizing properties.

Autologous immune complex glomerulonephritis induces abnormal embryonic development

Young female random-bred Wistar rats were immunized with homologous renal brush border membranes. The immunized animals exhibited all the clinical and immunopathological characteristics of chronic autologous immune complex glomerulonephritis (Heymann nephritis) closely resembling the idiopathic membranous glomerulonephritis in humans. The animals were subsequently mated. Congenital malformations and fetal growth retardation were observed in the offspring of the nephritic mothers; high incidence of embryonic/fetal resorptions was also observed. The types of anomalies were microphthalmia, cataractic lens, abnormal retina, micrognathia, cleft palate, lordosis, fetal edema, variable hemorrhage, omphalocele, syndactaly and cryptochidism. The most frequently observed anomaly was associated with the eye. Immunofluorescent studies indicated that no rat IgG was detected in the extraembryonic membranes, embryo or fetuses. Rat complement C3 was also absent around the conceptuses. The pathophysiologic mechanism leading to such deleterious embryonic/fetal effect is not clear.