ALBERT

Description: It is possible to produce fluorescence of erythrocytes as the result of specific antigen-antibody reactions of various blood group antigens; thus far, the factors A and B, a variety of Rh antigens and Kidd, have been successfully demonstrated with this method. It is important to realize that in the presence of adequate negative controls, low intensity fluorescence like that obtained with Rh antigens is nevertheless specific in systems involving erythrocytes. The method discriminates between A1 and A2 cells. More antibody must be attached to the red cell for fluorescence than for agglutination. The relative paucity of antigenic sites of Rh substance as compared to A and B antigens is reflected by the difference in intensity of fluorescence. The fluorescent antibody technic has been used successfully for the demonstration, and, to some extent, quantitation of minor cell populations in in vitro mixtures and in vivo. Injected Rh-positive erythrocytes were demonstrated in the blood of an Rh-negative volunteer during a period of 20 days. Fetal Rh-positive erythrocytes were demonstrated in several Rh-negative women, both with and without antibody, in the last trimester of gestation.

Description: 1. Fetal cells were demonstrated postpartum in approximately 20 per cent of Rh positive mothers with ABO incompatible infants and in only approximately 5 per cent of Rh negative mothers with both ABO and Rh incompatible infants in the absence of sensitization or presensitization. 2. When the prenatal findings were combined with those postpartum, the incidence was considerably greater in both groups (52 per cent and 32 per cent, respectively). 3. Two cases of massive transplacental hemorrhage in heterospecific pregnancies are reported with almost a normal survival of a few cells postpartum. 4. Observations on protective mechanisms bearing on isoimmunization in heterospecific pregnancies are made.

Description: A critical evaluation and discussion of certain technical aspects of the acid elution method and the immunofluorescent technic for the demonstration of fetal erythrocytes in maternal blood is presented. With appropriate precautions a close agreement between the two methods was obtained. Using one or both methods as applicable, base line data concerning transplacental passage were obtained in 622 unselected women, compatible with their offspring in the ABO system and not sensitized against the Rh factor. The intermittent entry of fetal erythrocytes into the maternal blood in small quantities was found to be a physiologic event. Postpartum, fetal erythrocytes were demonstrated in 50 per cent of the mothers. In approximately 10 per cent of the series, large fetal losses estimated to range from 0.5 to 40 ml. were observed. Massive transplacental hemorrhage was detected in nearly 1 per cent of the cases by examination of the maternal blood and usually but not always by overt anemia in the fetus. It was found to be the cause of stillbirth in one case. The evidence suggested that fetal bleeds usually began well before the onset of labor. Though labor itself under pathologic circumstances may be associated with transplacental hemorrhage, under ordinary conditions it was found to be of little or no significance with regard to the entry of fetal erythrocytes into the maternal circulation. Survival of fetal erythrocytes in the maternal circulation after delivery was generally found to correspond to the expected life span of red corpuscles. Apparent shortening of survival observed in several instances was probably due to the occurrence of the original spill some time before delivery. In two instances persistence of fetal erythrocytes well beyond the normal life span was observed. Both cases involved massive transplacental hemorrhage and fetal anemia with marked erythroblastemia, and mother and child were compatible to an exceptional degree with respect to blood group factors. The findings suggested the successful transplant of replicable erythroid precursor cells from fetus to mother with prolonged maternal tolerance, an interpretation supported by the results of skin homografts from offspring to mother in one case. The implications of these findings are discussed.