Jk3 alloantibodies during pregnancy-blood bank management and hemolytic disease of the fetus and newborn risk

BACKGROUND

The Kidd-null phenotype, Jk(a-b-), occurs in individuals who do not express the JK glycoprotein. Jk(a-b-) individuals can make an antibody against the Jk3 antigen, a high-incidence antigen present in more than 99.9% of most populations. This presents many challenges to the blood bank including identification of the antibody, masking of other antibodies, and how to provide transfusion support given the rarity of Jk3-negative blood products. Kidd antibodies may cause acute and delayed hemolytic reactions as well as hemolytic disease of the fetus and newborn (HDFN). In this article, we present a series of four practical cases of pregnant women with the anti-Jk3 alloantibody that demonstrate a range of clinical presentations of Kidd-related HDFN.

STUDY DESIGN AND METHODS

We retrospectively reviewed the clinical and blood bank records for four patients and their newborns encountered at institutions in Tennessee, Missouri, Hawaii, and Guam with an anti-Jk3 identified during pregnancy.

RESULTS

Two cases showed no significant evidence for HDFN, while two cases were of mild-to-moderate severity requiring early delivery due to elevated middle cerebral artery (MCA) flow velocities but requiring only phototherapy for hyperbilirubinemia. No intrauterine or neonatal transfusions were necessary. Anti-Jk3 alloantibody titers ranged from 2 to 128.

CONCLUSION

Clinical manifestations of anti-Jk3 HDFN are generally mild to moderate. Anti-Jk3 titers were not found to correlate directly with HDFN severity. We suggest a titer of 16 to 32 as a cutoff for implementing enhanced monitoring of fetal MCA flow velocities, as such titers may be indicative of elevated HDFN risk.

The Kidd (JK) Blood Group System

The Kidd blood group system was discovered in 1951 and is composed of 2 antithetical antigens, Jk^a and Jk^b, along with a third high-incidence antigen, Jk3. The Jk3 antigen is expressed in all individuals except those with the rare Kidd-null phenotype. Four Kidd phenotypes are therefore possible: Jk(a+b-), Jk(a-b+), Jk(a+b+), and Jk(a-b-). The glycoprotein carrying the Kidd antigens is a 43-kDa, 389-amino acid protein with 10 membrane-spanning domains which functions as a urea transporter on endothelial cells of the renal vasa recta as well as erythrocytes. The HUT11/UT-B/JK (SLC14A1) gene encoding this glycoprotein is located on chromosome 18q12-q21. The Jk^a and Jk^b antigens are the result of a single-nucleotide polymorphism present at nucleotide 838 resulting in an aspartate or asparagine amino acid at position 280, respectively. The Kidd blood group can create several difficult transfusion situations. Besides the typical acute hemolytic transfusion reactions common to all clinically relevant blood group antigens, the Kidd antigens are notorious for causing delayed hemolytic transfusion reactions due to the strong anamnestic response exhibited by antibodies directed against Kidd antigens. The Kidd-null phenotype is extremely rare in most ethnic groups, but is clinically significant due to the ability of those with the Kidd-null phenotype to produce antibodies directed against the high-incidence Jk3 antigen. Anti-Jk3 antibodies behave in concordance with anti-Jk^a or anti-Jk^b possessing the capability to cause both acute and delayed hemolytic reactions. Antibodies against any of the 3 Kidd antigens can also be a cause of hemolytic disease of the fetus and newborn, although this is generally mild. In this review, we will outline the makeup of the Kidd system from its historical discovery to the details of the Kidd gene and glycoprotein, and then discuss the practical aspects of Kidd antibodies and transfusion reactions with an extended focus on the Kidd-null phenotype. We will end with a brief discussion of the donor aspects related to the screening and supply management of blood from donors with the rare Jk(a-b-) phenotype.

Importance of Direct Antiglobulin Test (DAT) in Cord Blood: Causes of DAT (+) in a Cohort Study

BACKGROUND

The direct antiglobulin test (DAT) is the cornerstone of the diagnosis of hemolytic disease of the newborn (HDN). The aim of this study was to review the incidence and causes of positive DAT in cord blood in relation to development of HDN.

METHODS

We retrospectively reviewed all results of DAT, which is routinely performed in cord blood samples, along with the laboratory and infants' medical records.

RESULTS

DAT was positive in 70/2695 (2.59%) cases. In 64/70 (91.43%) cases, DAT positivity was attributed to ABO incompatibility. There were 50/218 (22.93%) DAT (+) cases in the A/O group and 13/97 (13.40%) cases in the B/O group (p = 0.0664). Two DAT (+) cases were attributed to maternal alloimmunization (anti-Fya and anti-JKb, respectively), and one to maternal IgG autoantibodies that developed after methyldopa treatment. Among the 70 DAT (+) cases, 30 (42.86%) cases required phototherapy with no difference between the A/O and B/O groups. The duration of phototherapy in the B/O group was significantly longer than in the A/O group (p = 0.024). There was a trend of correlation of increasing strength of DAT positivity with phototherapy need. No false positive DAT case was detected.

CONCLUSIONS

Although ABO incompatibility remains the main reason of DAT (+), other causes (e.g., alloimmunization, drugs) should also be explored. The relevant impact of DAT (+) on HDN development should be considered.

Hemolytic disease of the newborn due to anti-jkb: case report and review of the literature

Although anti-Jkb is a well-defined cause of severe acute or delayed hemolytic transfusion reactions, it is rarely associated with severe Hemolytic Disease of the Newborn (HDN), even with high antibody titer. To date, only 13 cases have been reported, so the possible reasons for that still remain unclear. Most of HDN due to anti-Jkb are mild-to-moderate, and usually have a good prognosis. A 41-years-old woman, who had a positive antibody screening test in her 13th week of pregnancy, was sent to the blood bank for study before an amniocentesis. Antibody identification and red blood cell (RBC) phenotyping of the patient and his husband were performed, plus arrays study in the amniotic fluid. An anti-Jkb was identified in the patient's serum with a titer of 1:1, and her RBC phenotype was O Rh(D) positive, C(+), c(+), E(-), e(+), K(-), Jka(+), Jkb(-). The RBC genotype of the fetus was B Rh(D) positive, Jka(+), Jkb(+). Antibody titer remained stable and the pregnancy was uneventful. At birth, there was no need of phototherapy or exchange transfusion for the newborn and her Jk(b+) typing result was confirmed in a cord blood sample. Although most of HDN cases due to anti-Jkb have a good outcome, monitoring antibody titer should be done to prevent fatal complications. Furthermore, antenatal antibody screening should be performed in every pregnant woman irrespective of her Rh(D) antigen status in order to detect red cell alloimmunization to other clinically significant blood group antigens.

Clinical aspects of urea transporters

Jk antigens, which were identified as urea transporter B (UT-B) in the plasma membrane of erythrocytes, and which determine the Kidd blood type in humans, are involved in transfusion medicine, and even in organ transplantation. The Jk(a-b-) blood type is a consequence of a silent Slc14A1 gene caused by various mutations related to lineage. In addition, the specific mutations related to hypertension and metabolic syndrome cannot be ignored. Genome-wide association studies established Slc14A1 as a related gene of bladder cancer and some genotypes are associated with higher morbidity. This chapter aims to introduce the clinical significance of urea transporters.

Hemolytic disease of newborn due to anti-Jk b in a woman with high risk pregnancy

This case illustrates the importance of blood group antibodies in antenatal serology other than Rh system as a cause of hemolytic disease of newborn (HDN). In India, antenatal antibody screening is done at majority of transfusion centers in only Rh (D) negative mothers. In this multigravida woman with high risk obstetrical history, an antenatal antibody screening by indirect antiglobulin test (IAT) was not performed as she was Rh (D) positive. Postnatal work up for the pathological jaundice in the neonate revealed that red cell alloimmunization had occurred due to anti-Jk(b). We conclude that antenatal antibody screening should be done in all pregnant women irrespective of the D antigen status to detect and manage red cell alloimmunization to any other clinically significant blood group antigens.