[Ontogeny of the immune response in mice. I. Presence of IgG and alpha fetoprotein in the body fluids of mice of various ages].

Alpha protein and IgG were determined by radial immunodiffusion in Swiss mice, in the amniotic fluid, milk and serum of the mice at different ages (fetus, neonates, at the age of 5, 10, 15, 20, 25, 30, 35 and 40 days and adults). The highest alpha-protein concentrations were found in the fetal serum (0.20 mg/ml) ; after birth serum levels rapidly fell and at 20 days could no longer be detected ; it was present in the amniotic fluid and milk collected within the first 24 hours after birth. In contrast, IgG was found in small concentrations in the fetal serum (0.60 mg/ml) but increased with age after birth. This immunoglobulin was present in the amniotic fluid and mothers' milk for 15 days. The significance of the results is discussed.