Interaction between Placental Alkaline Phosphatase and ABO System Polymorphisms

Abstract

Abstract. Placental alkaline phosphatase is a polymorphic glycoenzyme, produced by the fetal part of the placenta, which is found at an early stage of gestation and in considerable amount in the maternal bloodstream. Previous studies have shown an interaction of this polymorphism with that of ABO system during intrauterine life. In the present study the relationship between placental alkaline phosphatase phenotype and feto‐maternal isoimmunization in the ABO system was investigated. Isoimmunization was defined by a positive direct Coombs test on cord blood and/or jaundice in the neonatal period. In infants incompatible with their mothers in the B group, the incidence of the above‐mentioned signs of isoimmunization was lower in the presence of allele PI f1 of placental alkaline phosphatase. This relationship was not found in infants of group A. The present observations suggest that placental alkaline phosphatase may play an important role in the maternal‐fetal immunological relationships.