New antibody in severe rhesus incompatible pregnancies: IgG-kappa antiplacental alkaline phosphatase.

As already found in other various diseases, a macromolecular alkaline phosphatase complex (HMW-AP) was also found in sera of two severe Rhesus-incompatible pregnancies complicated by ascites and fetal hydrops at delivery. This atypical complex was detected and isolated by agarose gel electrophoresis. Immunoelectrophoresis and heat inactivation of this HMW-AP complex revealed that it consisted of IgG of the kappa type and placental AP isoenzyme. The transitory presence of this immuncomplex is discussed. However, in all women with Rh-immunized complicated pregnancies, significant variations of neutrophil and serum AP activities were observed. A fall in AP activity and the presence of an antiplacental AP antibody in serum of women with complicated Rh immunization should be of value in assessing the prognosis of the disease.