Three patients were studied who had acquired hemolytic anemia during pregnancy. One patient had a relapsing hemolytic anemia of pregnancy with a negative direct antiglobulin test. Previously reported cases have been presumed to be antibody-mediated because of rapid destruction of transfused blood, transient hemolysis in the newborn, and a favorable response to corticosteroid therapy. Our findings with the complement-fixation antibody consumption (CFAC) test offer support for an immune pathogenesis, since we documented abnormal concentrations of IgG on the patient's red cells during pregnancy and also on a sample of cord blood. The hemolytic anemia responded partially t o prednisone during pregnancy and resolved postpartum. A repeat CFAC test postpartum revealed a marked reduction in the number of IgG molecules per red cell on the mother's cells, and IgG was no longer detectable on the infant's red cells.The other patients had serologic abnormalities characteristic of an autoimmune hemolytic anemia with an IgG warm autoantibody. The patients were followed closely during pregnancy because of previous reports of life-threatening morbidity in mothers, as well as stillbirths, neonatal death, and seriously affected infants. An amniocentesis was performed in one patient because of persistent hemolysis in spite of prednisone therapy. The mothers and their infants did well, but serologic abnormalities and mild hemolytic anemia persisted in both mothers. Therefore, an elective splenectomy was performed with significant improvement in both instances.

We have used the complement-fixing antibody consumption ( CFAC ) test to detect small concentrations of IgG on red blood cells from patients with hemolytic anemias that are not thought to be caused by an immune mechanism. Although patients with hereditary spherocytosis, pyruvate kinase deficiency, and mechanical hemolytic anemias generally had normal concentrations of IgG bound to their red cells (less than 25 molecules IgG per red cell), we found that 39/62 (63%) patients with sickle cell anemia had elevated values. These 39 patients had a mean of 195 and a maximum of 890 molecules of IgG per red cell. None of the patients had been transfused within the previous 90 days, and some had never been transfused. Direct antiglobulin tests were positive in only two instances and autoantibodies were not found in the serum of any patient. However, eluates from the red cells of 6 of 23 patients demonstrated antibody activity against all of a panel of normal red cells by the indirect antiglobulin test. There was no correlation between the number of IgG molecules on patients' red cells and the severity of their anemia, the incidence of painful sickle cell crises, the reticulocyte count, or with blood transfusion history. We conclude that further study of immunohematologic abnormalities in patients with sickle cell anemia is warranted, especially in view of previous reports in this population of patients with red cell autoantibodies, autoimmune hemolytic anemia, hemolytic transfusion reactions without detectable alloantibodies, and an association of some episodes of pain crises with immunologically mediated red cell destruction.

Current literature implies that haemolytic anaemia in infectious mononucleosis is regularly caused by the temporary production of high thermal amplitude cold agglutinins of anti-i specificity. More recently, Capra et a1 (1969) suggested interaction between IgG anti-i and anti-IgG antibodies as the cause of haemolytic anaemia in infectious mononucleosis. A detailed serologic evaluation of thrcc patients during moderate to severe haemolytic anaemia in infectious mononucleosis revealed high thcrmal amplitude anti-i in only one. This patient's direct antiglobulin test (DAT) was negative using anti-IgG but was 3 + using anti-C3 and -C4. The serum antibody titre against cord or adult Oi cells was 512 at 4°C and 4 at 31°C. The anti-i was inhibited by mercaptoethanol, and anti-IgG was not found in the patient's serum. Patient 2 had a negative DAT and patient 3 had a 2 + DAT using anti-C3 and anti-Cq. Anti-i was present only in low titre at 4°C and was unreactive at 2oOC. It was inhibited by mercaptoetlianol. These patients' sera contained anti-IgG antibodies. In none of our patients were warm autoantibodies detected. This data demonstrates that haemolytic anaemia in infectious mononucleosis is not necessarily associated with high thermal amplitude anti-i. Further, since the anti-i antibodies in patients 2 and 3 were of low titre, were inhibited by mercaptoethanol, and did not react at physiologic temperatures, the mechanism of haeniolysis in these patients does not seem related to the interaction of anti-IgG and IgG anti-i antibodies. Further work is necessary to clarify the mechanism of haemolytic anaemia in infectious mononucleosis.

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