Study on Rubella antibody of Newborn Baby

It　is required, for examination of rubella antibody in the test of congenital rebella syndrome of newborn baby, to determine whether the antibody is originated at the mother (IgG) or due to infection at the stage of embryo and fetus (Igm and IgG). Using a modified method for absorption of most IgG antibody to rubella virus with St. aureus proposed by J. Ankerst et al., the titers of HI antibodies to its virus in mothers and their newborn babies' sera before and after[ treatment with St. aureus were determined, and IgM　and IgA antibodies were also detected by immuno-diffusion method. Sera of 315 newborn babies and parts of their mothers (302 women) were examined. Among them sera 14 pairs of mothers and their babies were tested by both the methods of Ankerst and of fractionation by sucrose density gradient centrifugation. The results were as follows : (1) Absorption of the serous IgG antibody of newborn baby was most suitably achieved by using two amounts of cells of St. aureus, 0.05 g and 0.1 g, for each 0.3 ml of the serum pre-treated with kaolin and goose red blood cells. (2) Sera of newborn babies in which IgM antibody was detected after the absorption with St. aureus in the epidemic period of rubella were 3 out of 315 cases (mainly from the sera of umbilical cord blood). (3) With 14 cases of the newborn babies and their mothers who had been infected in both the baby and the mother in 3 cases, and 11 cases showed the antibody only in the mothers. On the basis of the results obtained in this study, the absorption method of the antibody by St. aureus may be recommended as a simple and useful technique for the detection of rubella IgM antibody in newborn baby. Rubella infection at the stage of fetus was not observed in many cases which mother had been infected with the rubella in a later half period of pregnancy. It is conceivable the process of virus penetration through the placenta might be blocked by some mechanism in this stage of pregnacy