MILD COURSE OF FETAL RH-D HEMOLYTIC-DISEASE DUE TO MATERNAL ALLOIMMUNIZATION TO PATERNAL HLA CLASS-I AND CLASS-II ANTIGENS

The patient is a pregnant women of African origin with a prior history of spontaneous abortion and newborn dystrophy. The investigation show ed an anti-Rh D antibody (IgG isotypes 1 and 3) with an indirect antig lobulin tube test (IAT) titre of 1:512. The monocyte monolayer assay ( MMA) proved clearly the interaction of Fc receptors with the maternal anti-D, and so a clinical significance was expected. In spite of this, no signs of severe haemolysis in the Rh-D-positive and direct antiglo bulin test-positive fetus could be observed. Furthermore, two HLA clas s I and II alloantibodies (anti-A10, anti-DR13) directed against pater nal and fetal antigens were detected in the serum of the gravida. Both antibodies showed an inhibitory effect on the in vitro phagocytosis c apacity of mononuclear cells expressing at least one of the correspond ing HLA antigens (immunophagocytosis inhibition (IPI) test). Thus, the mild course of haemolytic disease may be explained by an effective in hibition of the fetal mononuclear phagocyte system by maternal HLA cla ss I and/or class II antibodies resulting in a diminished destruction of anti-D-coated fetal red blood cells.