日本人経産婦に認められた抗Di<sup>a</sup>の2例

Abstract

During routine post natal screening, two examples of anti-Dia stimulated by pregnancies were were found. One of the antibodies caused hemolytic disease of the newborn.Case 1. Mrs. H. K., a Dia negative, 28-year-old Japanese woman, had no history of blood transfusion and had a healthy child. The routine antibody tests during her first pregnancy revealed no immunization. When her serum was tested again six months after the birth, anti-Dia with a titre of 1:2-1:4 against Di (a+b+) cells by the anti-globulin technique was detected. A year later the antibody in her serum was not detectable.Case 2. Mrs. K. O., a 35-year-old Japanese woman, was found to contain anti-Dia in her serum when a routine direct anti-globulin screening on the cord cells of her third child was found to be positive. She was Di (a-b+), and had never been transfused. Her first child was Di (a-b+), and her husband and second child were Di (a+b+). Primary antibody response may has been due to stimulation by her second pregnancy. The third child became jaundiced within three days of birth; serum bilirubin level at the fifth days was 16.0mg/100ml decreasing to 13.7mg/100ml at the sixth day. The child was placed under phototherapy and survived. The anti-Dia serum from Mrs. K. O. reacted best by the papain- and ficin-antiglobulin techniques using anti-IgG; the titre of which was 1:64-1:128 against Di (a+b+) cells, it was not denatured by 2-mercaptoethanol. The antibody was also detectable by the papainized or ficinized cells in saline (titre 1:2-1:4), but the antibody dit not combine the complement. In titration studies with five Di (a+b-) and five Di (a+b+) cell samples, the anti-Dia showed dosage effect; the titration scores were 38.2 (on the average) for Di (a+b-) and 28.2 for Di (a+b+), and the difference was significant (F0=23.4, P<0.01).Distribution of the Diego groups. Random 3, 425 blood samples from Japanese in and around Tokyo were tested for Dia and Dib antigens by one of the present authors (H. N.). The phenotypes and gene frequencies obtained are shown in Table 1. The agreement with expectation on the assumption of Hardy-Weinberg equilibrium was satisfactory.The chances of antibody-production by pregnancy and by transfusion are expected to be 0.04-0.08 for anti-Dia and 0.002 for anti-Dib. As far as we know, four examples of anti-Dia, including two examples described in this paper, and three examples of anti-Db- have been found in Japan, suggesting that the potency of Dia antigen is lower than that of Db-.