A new "private" blood factor, designated as Berrens, was demonstrated with the aid of an immune isoantibody which was found in a woman sensitized by previous transfusion of her husband's blood and by pregnancy. The antibody had a relatively high titer and produced hemolytic disease of the newborn in the second child, manifested as jaundice and anemia. The factor was present in four out of seven members of three generations: grandmother, husband, his sister, and second child. It was absent in the father of the husband, his wife, the first child, and in four hundred and forty-eight random bloods.
Husbands should not be used as donors of blood for their wives.
Tests for immune isoantibodies developing in pregnant women are incomplete unless red cells of the child and/or father are included as tests cells.