Hemolytic Disease of the Newborn Due to Anti-A₁

1. The authors report clinical, hematological and serological data in a case of A₁ iso-sensitization of pregnancy.

2. The mother’s serum displayed immune characters specific to A₁ cells immediately after delivery. On the 24th day post partum the specificity extended to A₂ cells.

3. The disease exhibited by the infant was very mildly hemolytic. It was marked by a deep jaundice, repeated alimentary vomiting and a progressive state of drowsiness. There was no anemia. The direct anti-globulin test was negative.

4. It is shown that the mildness of the hemolytic process in cases of placental transfer of immune anti-A or anti-B into the incompatible A or B fetus is probably dependent upon a peculiar "resistance" of the fetal cells. This may be demonstrated in vivo and in vitro. In the present case replacement transfusion with A₁adult blood resulted in its in vivo sensitization, detectable by the antiglobulin test and eventually leading to hemolytic anemia.