Rh Immune Globulin Prophylaxis Research Articles

Estimating the cost of Rh testing and prophylaxis in early pregnancy: A time-driven activity-based costing study

ObjectiveTo estimate the cost of Rhesus (Rh) testing and prophylaxis for first-trimester vaginal bleeding in the ambulatory setting. Study designWe used time-driven, activity-based costing to analyze tasks associated with Rh testing and prophylaxis of first-trimester vaginal bleeding at one hospital-based outpatient and two independent reproductive health clinics. At each site, we observed 10 patients undergoing Rh-typing and two patients undergoing Rh prophylaxis. We computed the costs of blood Rh-typing by both fingerstick and phlebotomy, cost of locating previous blood type in the electronic health record (available for 69.8% of hospital-based patients), and costs associated with Rh immune globulin prophylaxis. All costs are reported in 2021 US dollars. ResultsThe hospital-based clinic reviewed the electronic health record to confirm Rh-status (cost, $26.18 per patient) and performed a phlebotomy, at $47.11 per patient, if none was recorded. The independent clinics typed blood by fingerstick, at a per-patient cost of $4.07. Rh-immune globulin administration costs, including the medication, were similar across facilities, at a mean of $145.66 per patient. Projected yearly costs for testing and prophylaxis were $55,831 for the hospital-based clinic, which was the lowest-volume site, $47,941 for Clinic A, which saw 150 patients/month, and $185,654 for Clinic B, which saw 600 patients/month. ConclusionsRh testing and prophylaxis for first-trimester vaginal bleeding generates considerable costs for outpatient facilities, even for Rh-positive patients with a prior blood type on record. ImplicationsRh testing and prophylaxis for first-trimester bleeding generate considerable costs even for Rh-positive patients and those with a previously known blood type. These findings highlight the need to reconsider this practice, which is no longer supported by evidence and already safely waived in multiple medical settings in the United States and around the world.

A Korean family with RHD*DNT only detectable after anti-D alloimmunization.

Identification of DNT, a rare partial D, can be challenging, as it is difficult to distinguish from D+. This study aimed to identify DNT individuals by analyzing the DNT proband's family members, characterize DNT, and propose management strategies. Family members of the first Korean DNT proband were recruited. RHD genotyping was conducted, and weak D tests were carried out using several anti-D reagents. Three DNT individuals were identified among 6 family members, including 1 with an anti-D alloantibody. As DNT red cells exhibited strong reactivity with all anti-D clones, DNT was serologically indistinguishable from D+. Moreover, unusual serologic findings in DNT individuals only became apparent after anti-D alloimmunization. We recommend DNT individuals as candidates for Rh immune globulin prophylaxis during the perinatal period and transfusions with D- blood components. An anticipatory RHD genotyping is suggested for partial D family members to prevent potential partial D individuals from becoming alloimmunized.

Live birth prevalence of hemolytic disease of the fetus and newborn in the United States from 1996 to 2010

Hemolytic disease of the fetus and newborn (HDFN) is mediated by maternal alloantibodies, a consequence of immune sensitization during pregnancy with maternal-fetal incompatibility with ABO, Rhesus factor (Rh), and/or other red blood cell antigens. RhD, Kell, and other non-ABO alloantibodies are the primary cause of moderate to severe HDFN, whereas ABO HDFN is typically mild. HDFN live birth prevalence owing to Rh alloimmunization among newborns in the United States was last estimated to be 106 per 100,000 births in 1986. HDFN live birth prevalence owing to all alloantibodies was estimated to be 817 to 840 per 100,000 in Europe. There is a need for updated prevalence estimates in the United States and a better understanding of disease demographics, severity, and treatments. This study aimed to estimate the live birth prevalence of HDFN and the proportion of severe cases of HDFN in the United States, to describe the associated risk factors, and to compare the clinical outcomes and treatments among healthy newborns, newborns with HDFN, and newborns who are sick without HDFN using a nationally representative hospital discharge database. In this retrospective, observational cohort study, we used data from the 1996 to 2010 National Hospital Discharge Survey to identify live births, defined by inpatient visits with the newborn flag, with and without a diagnosis of HDFN across 200 to 500 sampled hospitals (≥6 beds) per year. Patient and hospital characteristics, alloimmunization status, disease severity, treatment, and clinical outcomes were evaluated. Frequencies and weighted percentages were calculated for all variables. Logistic regression was used to compare the characteristics between newborns with HDFN and other newborns using odds ratios. Of 480,245 live births identified, 9810 HDFN cases were recorded. When weighted to the United States population, this corresponded to a live birth prevalence of 1695 per 100,000 live births. Compared with other newborns, newborns with HDFN were more likely to be female, Black, living in the South (vs the Midwest or West), and treated at larger (>100 beds) and government-owned hospitals. ABO and Rh alloimmunization accounted for 78.1% and 4.3% of newborns with HDFN, respectively, whereas HDFN caused by other antigens, such as Kell and Duffy, accounted for 17.6% of the cases. Among newborns with HDFN, 22% received phototherapy, 1% received simple transfusions, and 0.5% received exchange transfusions or intravenous immunoglobulin. Newborns affected by HDFN caused by Rh alloimmunization were more likely to require medical interventions, including simple or exchange transfusions, and more likely to be delivered by cesarean delivery. Overall, HDFN was associated with a longer hospital length of stay in the neonatal intensive care unit when compared with healthy and other sick newborns, a higher rate of cesarean delivery, and a higher rate of nonroutine discharge than healthy newborns. Overall, the live birth prevalence of HDFN was higher than those previously reported, whereas Rh-induced HDFN live birth prevalence was similar to those previously reported. HDFN live birth prevalence owing to Rh alloimmunization decreased over time, likely because of continued Rh immune globulin prophylaxis. Treatment patterns for newborns with HDFN and the comparative clinical outcomes when compared with healthy newborns confirm the continued clinical needs of this population.

Cases of RhD variants RhD*DAU2/DAU6 and RhD*weak D type 4.1 in pregnant women in Saudi Arabia.

The D antigen is one of the most immunogenic and clinically significant antigens of the Rh blood group system due to its various genotypes that encode for more than 450 different variants. Accurate RhD typing and D variant identification is crucial specially in prenatal screening during pregnancy. Women with RhD -ve phenotype are eligible to Rh immune globulin (RhIG) prophylaxis for the prevention of anti-D alloimmunization and hemolytic disease of the fetus and newborn (HDFN). However, there are some women who possess RhD variant alleles, who are mistakenly grouped as RhD positive and considered not eligible for RhIG prophylaxis, putting them at risk of anti-D alloimmunization and consequently leading to HDFN during subsequent pregnancies. Here, we describe two cases of RhD variants DAU2/DAU6 and Weak D type 4.1 in obstetric patients who were grouped as RhD +ve with negative antibody screening during routine serologic testing. Weak/Partial D molecular analysis using genomic DNA Red Cell Genotyping (RCG) revealed that both patients had RhD variants, one of which DAU2/DAU6 allele associated with anti-D alloimmunization. According to routine testing neither patients received RhIG or transfusion. In this case report we document to our knowledge the first reported cases of RhD variants among pregnant women in Saudi Arabia.

Prevalence and specificity of clinically significant red cell alloantibodies in pregnant women - a study from a tertiary care hospital in Southeast Michigan.

BackgroundMaternal red cell IgG antibodies can cross the placenta and cause hemolysis of fetal red cells in case of antigenic differences between maternal and fetal RBCs, leading to hemolytic disease of the fetus and newborn (HDFN). Although the incidence of anti-D associated HDFN has drastically reduced with Rh immune globulin prophylaxis, HDFN due to other maternal red cell alloantibodies still remains a concern. Prevalence and specificities of clinically significant red cell alloantibodies in pregnant females have rarely been reported in the USA.MethodsA retrospective chart review was conducted to determine the prevalence and specificity of clinically significant red cell alloantibodies in pregnant females who delivered at Beaumont Hospital Royal Oak between May 1, 2017 and December 31, 2017. A total of 4548 pregnant females were screened using electronic medical records. One female above 50 years age and two females with invalid ABO type were excluded from the study per IRB approved protocol. The remaining 4545 pregnant females with a valid ABO/RhD type and valid red cell antibody screen were included.ResultsOut of the 4545 included females, 440 had a positive red cell antibody screen. Of these 440 females, 34 had clinically significant alloantibodies, giving an overall prevalence of 0.74%. Anti-E was the most frequently identified significant alloantibody followed by anti-K. The most prevalent significant alloantibodies in RhD positive and RhD negative females were anti-E and anti-K, respectively. Significant association (p-value <0.001) was found between RhD type and the presence of clinically significant alloantibodies amongst females with positive antibody screen.ConclusionOur study aims to reiterate the importance of maternal red cell antibody screening during early pregnancy to help identify and manage high-risk pregnancies. Minimizing the exposure of childbearing age females to incompatible red cell antigens through unnecessary transfusions can help reduce the incidence of red cell alloimmunization and the risk of HDFN.

Adherence to Rh Immune Globulin Prophylaxis Guidelines: An Audit of a Modern Obstetric Cohort [34Q

INTRODUCTION: There is excellent evidence for postpartum Rh immune globulin (RhIG) prophylaxis efficacy and effectiveness. Continued adherence to RhIG prophylaxis guidelines is essential in preventing Rh alloimmunization and hemolytic disease of the newborn. This study aimed to perform an audit of RhIG prophylaxis practice in a modern obstetric cohort. METHODS: A retrospective chart review of 451 consecutive deliveries of Rh-negative women at a single-site tertiary medical center was performed. Fisher exact test was used for statistical analysis. RESULTS: The prevalence of Rh negativity was 8.9%. Of the Rh-negative women eligible to receive postpartum RhIG, 97.7% received RhIG and 98.9% were screened for fetomaternal hemorrhage (FMH). Of the Rh-negative women ineligible for RhIG administration, 4.6% inappropriately received RhIG and 91.9% were incorrectly screened for FMH. Evidence of FMH was demonstrated in 26.6% of Rh-negative women. Additionally, 1.7% of Rh-negative women had evidence of excessive FMH requiring additional administration of RhIG. Patients with FMH were more likely to have evidence of maternal acute blood loss anemia (47.8% versus 32.9%, P &lt; .05). Mode of delivery was not associated with increased likelihood of FMH (P=.4). CONCLUSION: This audit revealed two key areas for improvement. First, the widespread practice of ordering an unnecessary laboratory test was identified. Second, the rates of failure to order RhIG and FMH screening were determined. Though multiple factors likely contribute to imperfect adherence to guidelines, RhIG prophylaxis has historically been physician-driven at our institution. Implementing a protocol-driven approach may improve adherence; however, further study will be necessary to determine a superior approach.

Obstetrics and gynecology physician knowledge of Rh immune globulin prophylaxis.

Previous studies have shown that more than 20% of laboratories would have recommended inaccurate doses of Rh immune globulin (RhIG) in hypothetical cases. Efforts have been made in educating laboratories in correct dosing calculations; however, obstetricians are most often responsible for ordering RhIG. The objective of this study was to assess knowledge of RhIG indications and dosing among obstetrics and gynecology (OB/GYN) physicians in the United States. An anonymous 17- question online survey was distributed to all OB/GYN resident and attending physicians affiliated with US residency training programs. A total of 165 surveys were collected, with 139 fully completed. Ninety-two percent of respondents correctly recognized the need for RhIG in D- patients with negative antibody screens. In a scenario of a fetomaternal hemorrhage (FMH) of 45 mL, only 22% of respondents correctly chose the appropriate RhIG dosage. Of those who were correct, 10% had correctly identified 30 mL as the amount of fetal whole blood covered by one dose of RhIG, while 48% incorrectly identified 15 mL (n=31). A total of 49.3% of respondents reported residency as the most recent formal training on RhIG dosing and 35% reported never (n=140). Our study found that OB/GYN physicians are knowledgeable regarding indications for RhIG immunoprophylaxis but were insufficient at calculating dosages in cases of FMH. More standardized education and training among OB/GYN physicians may decrease the risk of maternal alloimmunization, in part because RhIG dosage recommendations from laboratories are not standard practice.

Two cases of the variant RHD*DAU5 allele associated with maternal alloanti-D

Rh is a complex blood group system with diverse genotypes that may encode weak and partial D variants. Standard serologic analysis may identify clinically significant D variants as D+; nevertheless, individuals with these D variants should be managed as D- patients to prevent antibody formation to absent D epitopes. Variant identification is necessary during pregnancy to allow for timely and appropriate Rh immune globulin (RhIG) prophylaxis for hemolytic disease of the fetus and newborn (HDFN) as D alloimmunization can occur with some D variants. Here, we describe two cases of the RHD*DAU5 allele associated with maternal alloanti-D in patients of African ancestry. Two obstetric patients were initially serologically classified as D+ with negative antibody detection tests on routine prenatal testing. Repeat testing at delivery identified anti-D in both patients with no history of RhIG administration or transfusion. DNA sequencing revealed that both patients possessed the RHD*DAU5 allele. Cord blood testing on both infants revealed positive direct antiglobulin test (DAT) results with anti-D eluted from the red blood cells (RBCs) of one of the infants. Despite the positive DAT, neither infant experienced anemia or hyperbilirubinemia. We document two cases of pregnant women whose RBCs expressed a partial D variant and were classified as D+ on the basis of standard serologic testing, resulting in subsequent failure to provide RhIG prophylaxis. Both cases were associated with alloanti-D formation but without significant HDFN. To our knowledge, these are the first reported cases of maternal alloanti-D associated with the RHD*DAU5 partial D variant.

An investigation of secondary anti-D immunisation among phenotypically RhD-negative individuals in the Chinese population.

Despite the introduction of anti-D prophylaxis into clinical practice, RhD alloimmunisation remains a problem, particularly in the context of transfusions and pregnancy-induced alloimmunisation. The incidence of RhD alloimmunisation among phenotypically RhD-negative individuals is unknown in most countries. We investigated RhD alloimmmunisation in RhD-negative pregnant women and transfusion recipients in south-east China in order to optimise the prevention of this phenomenon. We analysed the RhD alloimmunisation status of RhD-negative pregnant women and transfusion recipients in south-east China. The RhD blood types of the study population were identified by standard serological methods. The D antigen was further tested with the indirect antiglobulin test to exclude or confirm weak D or partial D types. RhC, c, E and e antigens were typed in all subjects. If anti-D antibody screening was positive, the specificity and titre of the antibody were determined. The Del phenotype was investigated by the polymerase chain reaction sequence-specific primer method. An anti-D antibody was found in 61 of 416 RhD-negative pregnant women (14.66%), and in 11 of 227 RhD-negative transfusion recipients (4.85%). None of the 72 RhD-negative pregnant women or transfusion recipients with anti-D had the Del phenotype. Anti-D antibodies were not detected among Del phenotype individuals and Del phenotypes were not found in anti-D antibody producing individuals. Our study suggests that the risk of alloimmunity-induced neonatal haemolysis increases in true RhD-negative multipara. Perinatal protection would be necessary in these patients, while antenatal anti-D testing and Rh immune globulin prophylaxis would be unnecessary for RhDel pregnant women. Pregnant women and transfusion recipients with the Del type seldom produce anti-D antibody. RhD-negative recipients are not at risk of alloimmunisation after transfusion with Del red blood cells.

Management of first-trimester complications in the emergency department

The pharmacologic management and the nonpharmacologic management of first-trimester complications in the emergency department are reviewed. The obstetric complications most commonly seen in early pregnancy (less than 20 weeks' gestation) include ectopic pregnancy, threatened and inevitable abortions, and incomplete, complete, and missed abortions. The treatment options for ectopic pregnancy include expectant management, medical management with methotrexate, and surgery. If patients have signs and symptoms of tubal rupture, surgery must be performed immediately. In other cases, the choice of management technique is based on the patient's clinical condition, factors related to the ectopic pregnancy, and the patient's preferences. Pharmacologic therapies for women with confirmed threatened abortion include human chorionic gonadotropin, progesterone, uterine muscle relaxants, and Rh immune globulin prophylaxis. Treatment goals for women whose condition has advanced to inevitable abortion include evacuating any retained products of conception, either with expectant (conservative) management or pharmacologic or surgical intervention. The best treatment option is often determined by the mother's clinical status at the time of presentation and her preference of management strategy. Management of complete abortion may not require any further intervention; however, it is often difficult to identify a complete versus incomplete abortion. Treatment options for complete, incomplete, and missed abortions include expectant, surgical, and medical management. Ectopic pregnancy, threatened and inevitable abortions, and incomplete, complete, and missed abortions are common complications during early pregnancy. Various medical and surgical treatment options are available for managing these complications, including expectant management, medical management, and surgery.

Does Rh immune globulin suppress HLA sensitization in pregnancy?

How Rh immune globulin (RhIG) prevents sensitization to D antigen is unclear. If RhIG Fc delivers a nonspecific immunosuppressive signal, then RhIG may inhibit sensitization to antigens other than D. HLA antibody prevalence was compared in previously pregnant D- versus D+ women to investigate whether RhIG suppresses HLA sensitization. In the Leukocyte Antibody Prevalence Study (LAPS), 7920 volunteer blood donors were screened for anti-HLA and surveyed about prior pregnancies and transfusions. A secondary analysis of the LAPS database was performed. D- women not more than 40 years old (presumed to have received antenatal with or without postpartum RhIG in all pregnancies) had a significantly lower HLA sensitization rate than D+ women (relative risk, 0.58; 95% confidence interval [CI], 0.40-0.83). When stratified by deliveries (one, two, three, or four or more), D- women not older than 40 were HLA sensitized less often than D+ women in every case. In contrast, a clear relationship between D type and HLA sensitization was not seen in older previously pregnant women whose childbearing years are presumed to have preceded the use of routine RhIG prophylaxis. In a multivariable logistic regression model, D- women not more than 40 years old remained significantly less likely to be HLA sensitized compared with D+ women after adjusting for parity, time from last pregnancy, lost pregnancies, and transfusions (odds ratio [OR], 0.55; 95% CI, 0.34-0.88). Consistent with a nonspecific immunosuppressive effect of RhIG, younger previously pregnant D- women were less likely than previously pregnant D+ women to be HLA sensitized.

Antenatal Rh prophylaxis is unnecessary for “Asia type” DEL women

Background Generally Rh-negative patients need to be transfused with Rh-negative red blood cells. For pregnant women carrying Rh-positive fetus, the antenatal anti-D detection and Rh immunoglobulin prophylaxis are required worldwide. In East Asia, a RhD variant, termed “Asia type” DEL, was found in approximately 30% of apparent Rh-negative individuals. The antigenic and molecular properties of the DEL were previously defined. Few data discuss whether DEL could be immunized by D antigen clinically although DEL was reported arousing alloimmunization to true Rh-negative patients. Study design and methods To determine whether the DEL variant can be immunized to the D antigen, we retrospectively evaluated 104 Rh-negative pregnancies with allo-anti-D antibodies, and we also tracked 199 consecutive apparent Rh-negative pregnant women, with a history of gestations or parturitions but not subject to anti-D gamma-globulin prophylaxis, for evidence of allo-anti-D. The DEL variant was first excluded by ccee phenotypes and then identified through PCR analysis or sequencing. Results In the retrospective study, we expected to find 30 DEL variants, yet none of the anti-D alloimmunized women were DEL-positive. And in the second group, none of 44 DEL-positive women versus 38 of 155 (24.5%) true Rh-negative women (those excluding DEL) formed allo-anti-D. Conclusion The data indicate that the “Asia type” DEL variant does not appear at risk of alloimmunization to the D antigen. It strongly suggests that the antenatal Rh immune globulin prophylaxis is unnecessary for DEL women. Furthermore, it implicates that the “Asia type” DEL may be deemed Rh-positive safely for clinical transfusion therapy.

Prevalence of RhD variants, confirmed by molecular genotyping, in a multiethnic prenatal population.

RhD determination in pregnant women is critical to facilitate Rh immune globulin prophylaxis for RhD-negative women. A single amino acid change in the RhD antigen can cause epitope loss, giving rise to "partial D" variants. Women with some partial D variants may develop anti-D against the missing epitope after pregnancy. RBCs with partial D may type as D-positive or D-negative depending on the reagent used. We screened routine blood bank samples from 501 prenatal patients for RhD variants by 3 commercially available serologic methods. Discordant serologic results were found in 11 cases. Weak D (n = 5) and partial D (n = 5) variants were confirmed by molecular genotyping in all but 1 case. RhD variants, confirmed molecularly, occur in 2.2% of our multiethnic population. Consideration of patients' ethnic background and close cooperation between pathologists and obstetric providers facilitate optimal prenatal care in these cases.

Weak D prevalence among Indian blood donors

Weak D prevalence among Indian blood donors

Integrating Molecular Technologies for Red Blood Cell Typing and Compatibility Testing Into Blood Centers and Transfusion Services

Nucleic acid-based technology is now at a point where the field of transfusion medicine is ready for its widespread application. In the donor center, genotyping of red blood cell (RBC) products provides phenotype-matched products for special patient populations or antigen-negative products for patients with alloantibodies. In the immunohematology reference laboratory, molecular technologies aid in discerning blood types in the situation of a typing discrepancy and improve pretransfusion RBC testing reagents. In the hospital transfusion service, genotyping patients aids in providing phenotype-matched RBC products. In prenatal testing, genotyping for RHD aids in the decision for Rh immune globulin prophylaxis and predicting risk of hemolytic disease of the fetus and newborn. Before genotyping is accepted as the universal standard for pretransfusion and donor testing, important limitations of this technology must be addressed, including the fact that the genotype does not always predict the phenotype and the need for creating the ideal high-throughput platform. Clinical trials are needed to answer important questions, and a donor and patient database is needed. A stepwise plan for progressive introduction into the donor centers and transfusion services must be established. In conclusion, the field of transfusion medicine is ready to expand the use of molecular diagnostics.

Rh discrepancies caused by variable reactivity of partial and weak D types with different serologic techniques

RhD discrepancies between current and historical results are problematic to resolve. The investigation of 10 discrepancies is reported here. Samples identified were those that reacted by automated gel technology and were negative with an FDA-approved reagent. Reactivity with a commercially available panel of monoclonal anti-D was performed. Genomic DNA was evaluated for RHD alleles with multiplex RHD exon polymerase chain reaction (PCR), weak D PCR-restriction fragment length polymorphism, and RHD exon 5 and 7 sequence analyses. The monoclonal anti-D panel identified two samples as DVa, yet possessed the DAR allele. Two weak D Type 1 samples had a similar monoclonal anti-D profile, but only one reacted directly with one of two FDA-approved anti-D. Only two of four weak D Type 2 samples reacted directly with one FDA-approved anti-D, and their D epitope profile differed. The monoclonal anti-D reagents did not distinguish between partial and weak D Types 1 and 2. Weak D Types 1 and 2 do not show consistent reactivity with FDA-approved reagents and technology. To limit anti-D alloimmunization, it is recommended that samples yielding an immediate-spin tube test cutoff score of not more than 5 (i.e., < or =1+ agglutination) or a score of not more than 8 (i.e., < or =2+ hemagglutination) by gel technology be considered D- for transfusion and Rh immune globulin prophylaxis. That tube test anti-D reagents react poorly with some Weak D Types 1 and 2 red cells is problematic, inasmuch as they should be considered D+ for transfusion and prenatal care. Molecular tests that distinguish common partial and Weak D types provide the solution to resolving D antigen discrepancies.

Antenatal administration of Rh‐immune globulin causes significant increases in the immunomodulatory cytokines transforming growth factor‐β and prostaglandin E2

Production of specific cytokines in response to administration of Rh-immune globulin (RhIG) was examined to assess the mechanism of inhibition of the anti-D production and prevention of hemolytic disease of the newborn (HDN). Plasma levels of 17 different cytokines before and 48 hours after antenatal administration of anti-D were measured in 10 women candidates for prophylaxis with RhIG. No striking changes were observed in levels of the cytokines interleukin (IL)-1 sRII, IL-12 p40, IL-16, or monocyte chemoattractant protein-1. Levels of IL-4, -5, -10, -13, and -17; macrophage inflammatory protein-1alpha; granulocyte-macrophage-colony-stimulating factor; tumor necrosis factor-beta; and interferon-gamma remained below detection levels both before and after testing. IL-1ra levels, however, showed a slight to moderate decrease in 7 of 10 women after RhIG administration. In contrast, levels of TGF-beta1 increased more than 1.3-fold in 7 of 10 women and more than 2-fold in 4 of 10 women; in 1 instance the increase was more than 5-fold and this woman also had a significant increase in TGF-beta2. In addition to TGF-beta, 5 of 10 women had a modest increase (>1.5-fold) in prostaglandin E2 (PGE2). Analyses of the combined results of the 10 women showed that increases in both TGF-beta1 and PGE2 after RhIG were significant. These results indicate that RhIG prophylaxis can induce higher than baseline levels of two strongly immunomodulatory cytokines, TGF-beta and PGE2. These findings represent one possible mechanism for the inhibition of the primary immune response to the D antigen in women receiving RhIG prophylaxis for prevention of HDN.

The Mechanism of Rh-Immune Globulin Prophylaxis Involves Significant Increases in the Immunosuppressive Cytokines TGFβ and PGE2.

For more than 40 years, hemolytic disease of the newborn (HDN) caused by anti-Rh(D) antibody produced by a pregnant mother to her Rh(D)+ baby has been prevented by Rh(D)-immune globulin prophylaxis. Surprisingly, although a number of theories have been proposed, the mechanism of action of this immunosuppressive treatment remains completely unknown (Kumpel BM, Immunol Lett. 2002; 82:67–73). One potential mechanism of action is the production of one or several strongly immunosuppressive cytokines capable of blocking a primary immune response. Thus, to begin to unravel the possible mechanism(s) of the immunosuppression induced by administration of Rh(D)-immune globulin, we have examined production of a number of immunomodulatory cytokines following administration of Rh(D)-immune globulin. After informed consent, we measured levels of 17 different cytokines pre- and 48 hours post-administration of 300 μg of anti-Rh(D)(WinRhoSDF) in 10 healthy women candidates for Rh(D)-immune globulin prophylaxis. We used platelet-poor plasma from citrated whole blood and quantitative ELISA having the most sensitive detection limits. We observed no striking changes in levels of the cytokines IL-1 sRII, IL-12 p40, IL-16, or MCP-1. Levels of IL-4, IL-5, IL-10, IL-13, IL-17, MIP-1α, GM-CSF, TNFβ, and IFNγ remained below detection levels both pre- and post-testing. However, IL-1ra levels showed a slight to moderate decrease in 7 of 10 women after Rh(D)-immune globulin administration. In contrast, levels of TGFβ-1 increased, >1.3-fold in 7 of 10 women and >2-fold in 4 of 10 women. In one instance, the increase in TGFβ-1 (42, 855 pg/mL) was >5-fold and this woman also had a significant increase in TGFβ-2 (352 pg/mL). In addition to TGFβ, 4 of 10 women had increases of >1.5-fold in PGE2. Statistical analyses using ANOVA, paired Student's t-test, and Wilcoxon signed-rank, for the combined results of all 10 women receiving Rh(D)-immune globulin indicated that only TGFβ and PGE2 were significantly elevated post administration of Rh(D)-immune globulin. These results indicate that Rh(D)-immune prophylaxis can induce high levels of the strongly immunosuppressive cytokines TGFβ and PGE2. Both of these molecules have been shown to induce profound immunosuppression including prevention of primary immune responses (Ludviksson BR, et al., Eur J Immunol. 2000; 30:2101–2111; Zhou H, Lamont SJ, Int J Fertil. 1986; 31:305–310). Our findings represent the first clear evidence for a mechanism of action of Rh(D)-immune prophylaxis.

Reactivity of FDA-approved anti-D reagents with partial D red blood cells

Abstract Individuals whose RBCs are characterized as having a partial D phenotype may make anti-D if exposed to normal D+ RBCs; thus it is desirable that they be typed as D– should they require blood transfusion or Rh immune globulin (RhIG) prophylaxis. Further, use of different anti-D reagents by blood centers and transfusion services can account for FDA-reportable errors. For this study, anti-D reagents for use in tube tests were obtained from three U.S. manufacturers. They included three examples of IgM monoclonal anti-D blended with monoclonal IgG anti-D, one IgM monoclonal anti-D blended with polyclonal IgG anti-D, and two reagents formulated with human anti-D in a high-protein diluent. One anti-D formulated for use by gel column technology was also tested. Direct agglutination tests by tube or gel were strongly positive (scores 9–12), with partial D RBCs of types DII, DIIIa, DIIIb, and DIVa. No reagent anti-D caused direct agglutination of DVI type 1, DVI type 2, or DFR phenotype RBCs. One tube anti-D reagent formulated with an IgM monoclonal anti-D plus a polyclonal IgG anti-D failed to cause direct agglutination of DVa, DBT, and R0 Har RBCs, while DVa RBCs reacted weakly with two high-protein reagents formulated with human IgG anti-D. In contrast, the anti-D used by gel column technology was strongly reactive (score 11) with DVa, DBT, and R0 Har RBCs. The single monoclonal IgM–polyclonal IgG blended anti-D and the two high-protein reagents were also the only reagents that failed to react with R0 Har RBCs by the IAT. Elimination of the test for weak D on all patient samples, using currently available FDA-licensed reagents, will ensure that partial D category VI (DVI) patients will type as D– for the purpose of RhIG prophylaxis and blood transfusion. However, RBCs of other partial D phenotypes will be classified as D+ in direct agglutination tests with some, if not all, currently available reagents. Testing donors for weak expression of D continues to be required, albeit that Rh alloimmunization by RBCs with a weak or partial D phenotype is uncommon. Further, because of differences in performance characteristics among FDA-approved reagents, conflicts between donor center D typing and transfusion service confirmatory test results are inevitable. Immunohematology 2005;21:146–8.

Red Blood Cell Alloimmunization: Principles and Management in Pregnancy

Despite significant advances in immunohematology, including the discovery of the Rhesus factor and the subsequent development of nationwide Rh immune globulin prophylaxis programs, the incidence of Rhesus alloimmunization is one to two per 1000 Rh-negative women. This is largely due to the lack of administration of Rh immune globulin in high risk situations. The identification of a sensitized pregnant patient requires an initial antibody screen with appropriate antibody titres and paternal red blood cell antigen pheno-typing. Fetuses, identified at high risk due to critical antibody titre levels, require invasive action with serial amniocenteses plus amniocyte antigen testing. Percutaneous umbilical blood sampling or intrauterine fetal transfusion may be dictated in severe situations.