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A 35-year-old Brazilian woman (gravida 4, para 2) was delivered of a severely anaemic child whose cord red blood cells had a strongly positive direct antiglobulin test and who required two exchange transfusions within 24 h of birth. Because of the emergency of the situation and the lack of a local immunohaematology reference laboratory, the phenotype of the mother and the specificity of the relevant antibody could not be determined. Hence, compatible blood was not immediately available and the infant had to be given repeated exchange transfusions with incompatible group 0 Rh-negative blood. The infant is now healthy and thriving. The mother's red cells were subsequently found to lack all the antigens of the Rh system, and her serum reacted with all red cell samples except those of two unrelated Rhnull individuals. Her serum gave high titres (i.e. 1,024–4,096) by the indirect antiglobulin test against red cells of normal Rh phenotype, as well as against cells with partially deleted Rh phenotypes (titres = 128–512 with –D–·/–D– and ·D·/·D· samples, respectively), and was extremely active in antibody-dependent cell-mediated cytotoxicity and monocyte monolayer assays against red cells of normal Rh phenotypes.

Summary. In 40 cases of haemolytic disease of the fetus due to RhD immunization where the fetus required intrauterine transfusion, fetal packed cell volume was compared with the following parameters of maternal anti-D: (a) concentration, (b) IgG subclass, (c) activity in a macrophage binding assay, and (d) activity in a monocyte antibody-dependent cell mediated cytotoxicity (ADCC) assay. The anti-D concentration exceeded 4 iu/ml in all cases, correctly indicating the risk of haemolytic disease. A relationship between IgG subclass composition of the anti-D and severity of anaemia was not observed; IgGl, IgG3 and IgG 1 + 3 antibodies were all detected. The AuCC assay gave the best correlation between assay results and fetal packed cell volume: high results correctly indicated fetal anaemia in 95% of cases. Macrophage binding assay results were only considered as high in 70% of cases. Overall, these results indicate that serological tests and bioassays in highly immunized mothers may not generate any information that proves more useful than ultrasonography and their previous obstetric history.

Sera containing anti-D, taken from 44 RhD-negative women with RhD-positive infants, were tested in antibody-dependent cellular cytotoxicity (ADCC) and monocyte monolayer assays (MMA) which used similar target and effector cell populations. In addition, the anti-D concentration was measured in the Auto Analyzer and the number of IgG1 and IgG3 anti-D molecules bound to the target red cells was measured by flow cytometry. The results of the functional assays and Auto Analyzer quantitation were examined for correlation with IgG subclass quantitation and all results were compared for their ability to predict the severity of haemolytic disease of the newborn (HDN). ADCC correctly predicted HDN in 39/44 (88.6%) cases, Auto Analyzer quantitation in 35/44 (79.5%) and the MMA in 32/44 (72.7%). For all three assays, the number of correct predictions was highest when the maternal serum contained both IgG1 and IgG3 anti-D. ADCC activity and HDN were correlated with the number of cell-bound IgG1 molecules (r > or = 0.58), but MMA activity was most closely correlated with the number of cell-bound IgG3 molecules (r = 0.68). Hence the superior predictive value of ADCC is due to its ability to reflect the IgG1 component of maternal anti-D, which has a better correlation than IgG3 anti-D with the severity of HDN.

Anti-Sc1 was detected in a gravida-2 patient at 12 weeks' gestation. At 29 weeks, the antibody was found to be of the IgG3 subclass with a titer of 16, score 36, by the indirect antiglobulin test, and it produced 7 percent lysis by antibody-dependent cellular cytotoxicity (ADCC) assay, a finding that suggested an unaffected fetus. The titer remained constant throughout the pregnancy, as did the IgG subclass and activity in the ADCC assay. At delivery of the full-term infant, the cord hemoglobin was 13.5 g per dL and the direct antiglobulin test was positive (3 +) with anti-IgG. The infant did not require transfusion. A sample taken 9 weeks after delivery showed 44 percent lysis in the ADCC assay. The anti-Sc1 titer was 32, score 65.

Summary Macrophages obtained from human monocytes by monolayer culture were stimulated with recombinant immune interferon. They were compared with unstimulated macrophages and monocytes as indicator cells in the mononuclear phagocyte assay, using both IgG anti-Rh(D)-coated complement-coated red cells. The presence of the interferon in the culture medium improved the adherence of macrophages in monolayers. The interferon.markedly augmented the number of IgG-coated red cells which became attached to the macrophages and reduced the amount of antibody needed for red cell-macrophage interaction. This stimulatory effect occurred regardless of the IgG subclass composition of the anti-Rh(D) antibody. The activity of the stimulated macrophages to interact with IgG- or complement-coated red cells was considerably greater than that of monocytes. The results imply that macrophages treated with recombinant immune interferon are more sensitive than monocytes as indicator cells in the mononuclear phagocyte assay.