[Immunohistochemical determination of maternal and child blood groups (ABO) in mature placental tissue].

Using the indirect immunoperoxidase technique (PAP method), ABO characteristics of mother and child were correctly identified in tissue specimens from 10 mature human placentas. In one case, a weak infantile A reaction was overlooked in the agglutination test but correctly identified by immunohistochemistry. In accordance with the weak expression of ABO characteristics in cord blood, immunohistochemical labeling of infantile erythrocytes with monoclonal and human antibodies, as well as Ulex europeaeus agglutinin I (UEA I), was less pronounced than that of mature erythrocytes. Labeling of the chorionic vessel endothelium, in contrast to that of adult endothelial tissue, was negative with anti-A or anti-B but, regardless of the infantile blood group, pronounced with UEA I. Regular identification of the blood groups was possible in decomposed placental tissue stored at room temperature for 1 week, but not in tissue stored for 2 or more weeks.