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The severity of the hemolytic disease of the fetus and newborn (HDFN) due to Jra mismatch ranges from no symptoms to severe anemia that requires intrauterine and exchange transfusions. We encountered a newborn, born to a healthy mother having anti-Jra at 38 weeks of pregnancy, who had moderate anemia, a positive direct antiglobulin test (DAT) result, no increased erythropoiesis, and no jaundice at birth. Flow cytometry revealed that the Jra antigen of red cells in the infant was nearly negative at birth, biphasic at 5 weeks, and lowly expressed at 7 months of life. We searched online for previous case reports on HDFN due to Jra incompatibility. Among 63 reported cases, excluding 25 cases, 38 were included with the present case for analysis. Of 39 newborns, 10 developed clear anemia (hemoglobin <10.0 g/dL), and 1 died, 5 developed hydrops fetalis, 4 needed intrauterine transfusion and/or exchange transfusion, and 3 received red cell transfusion after birth; overlaps were included. Among 29 neonates with no anemia, 8 needed interventions including phototherapy and γ-globulin infusion, and the remaining 21 received conservative supports only. The maternal anti-Jra titer, ranging between 4 and 2048, did not correlate with the severity of anemia, levels of bilirubin, or any interventions required. The DAT of red cells was positive in 29 of 36 fetuses/newborns tested, whereas it was often negative among anemic neonates (4 of 9) (P <.05). Hematopoiesis did not increase effectively, as indicated by reticulocyte ratios between 1.7% and 22.3%, even with the increase in reticulocytes in anemic neonates compared with nonanemic neonates (P <.05). Total bilirubin levels ranged broadly between 0.2 and 14.3 mg/dL but were generally low. The maternal anti-Jra titer and IgG3 subclass did not correlate with the morbidity of the newborns. Being identical/compatible between mothers and their infants may possibly enhance infants' morbidity, as a weak tendency was observed (P =.053). Maternal anti-Jra may suppress erythropoiesis in fetuses via a mechanism different from the established HDFN, such as anti-D, as evidenced by the lower reticulocyte count and small increase in bilirubin in neonates. As the anti-Jra titer, IgG subclass, and DAT were not correlated with the severity, the mechanism of anti-Jra–induced HDFN remains to be elucidated. • Of 39 reported newborns born to mothers with anti-Jra, only 10 developed anemia and many did not need interventions. • Maternal anti-Jra titer or IgG3 subclass, and newborn's direct antiglobulin test did not correlate with the morbidity of the neonates. • Hematopoiesis of the affected neonates did not increase effectively. • Anti-Jra may suppress fetal erythropoiesis via mechanism different from the established HDFN. [ABSTRACT FROM AUTHOR]

Abstract: We encountered a broadly reactive red cell alloantibody in 1991, reacting unlike any other known antibody, and named it anti-KANNO after the first patient. A total of 28 cases of anti-KANNO in the Japanese literature were reviewed. To distinguish KANNO from other antibodies against high-frequency antigens, including anti-JMH, anti-Ch/Rg, and anti-Jra, we conducted serologic studies with proteolytic enzyme and chemical treatments, complement sensitization against red cells, and serum neutralization techniques. Reactivity of anti-KANNO against red cells lacking high-frequency antigens and antisera to high-frequency antigens against KANNO cells were tested. Among the 28 patients, 26 were female, of whom 25 had a history of pregnancy. Red cells from patient KANNO were reactive with antisera against antigens of high frequency. Anti-KANNO reacted weakly with all cells known to lack high-frequency antigens. It reacted with 2-aminoethylisothiouronium bromide, so it can be distinguished from anti-JMH. Differences among anti-KANNO, anti-Ch/Rg, and anti-Jra emerged with enzyme-treated cells, complement-sensitized cells, and the addition of normal serum. As yet, there are no reports of hemolytic transfusion reaction or hemolytic disease of the fetus and newborn attributable to anti-KANNO. It appears that anti-KANNO is a newly characterized antibody more likely stimulated by pregnancy than by transfusion and with little or no clinical significance. Further surveillance and investigation of anti-KANNO, its antigen biochemistry, and its genetics are warranted. [Copyright &y& Elsevier]