Identifying obstetrics patients in whom RHD genotyping can be used to assess risk of D alloimmunization

The D antigen is highly immunogenic and may cause alloimmunization to occur after blood transfusion or pregnancy. Some RHD variant alleles express a D antigen that is missing one or more epitopes, thus putting a presumed D+ patient at risk for alloanti-D and hemolytic disease of the fetus and newborn. It is generally accepted that individuals who have a serologic weak D phenotype due to one of three alleles common in Caucasians, RHD*weak D types 1, 2, or 3, are not at risk for alloimmunization. In this study, blood samples from 46 obstetrics patients from a local health system were identified based on discrepant results between automated gel and manual tube testing (n = 20) or based on presentation with a serologic weak D phenotype (n = 26). RHD genotyping was performed using commercial and laboratory-developed tests. Of the 26 serologic weak D samples, 18 (69.2%) were found to carry alleles RHD*weak D type 1, 2, or 3. The remaining eight samples (30.8%) were found to carry partial D alleles. Of the 20 samples submitted because of D typing discrepancy, 7 (35%) carried alleles RHD*weak D type 1, 2, or 3, while 13 (65%) carried partial RHD alleles. This report summarizes the findings of one hospital system and its approach to integrating RHD genotyping into its assessment of risk of alloimmunization in obstetrics patients. It demonstrates that individuals with partial RHD alleles can present with serologic weak D phenotype, such that, without RHD genotyping, these individuals may not be identified as candidates for Rh immune globulin. The study also demonstrates that use of two methods (automated gel and tube testing) allows for identification of partial D cases that would otherwise be missed. I.

Predicting anti-RhD titers in donors: Boostering response and decline rates are personal

Background

Anti-RhD immunised donors provide anti-RhD immunoglobulins used for the prevention of rhesus disease. These donors are periodically hyper-immunised (boostered) to retain a high titer level of anti-RhD.

Study design and methods

We analysed anti-RhD donor records from 1998 to 2016, consisting of 30,116 anti-RhD titers from 755 donors, encompassing 3,372 booster events. Various models were fit to these data to allow describing the anti-RhD titers over time.

Results

A random effects model with a log-linear anti-RhD titer decline over time and a saturating titer response to boostering is shown to fit the data well. This model contains two general model parameters, relating timing and maximum of the booster effect, as well as two parameters characterizing the individual donor, namely how fast the booster effect saturates with current titer and the anti-RhD decline rate. The average individual log₂ decline is 0.55 per year, i.e. a 32% decline in absolute titer, with half of the donors declining between 13% and 41% per year. Their anti-RhD titer peaks around 26 days following a booster event. Boostering response reduces with higher titers at boostering; at median titer (log₂ 11) the mean increase per booster is log₂ 0.38, that is from an absolute titer of 2048 to 2665 (+30%), with half of all donors increasing between 16% and 65% in their titer.

Conclusion

The model describes anti-RhD titer change per individual with only four parameters, two of which are donor specific. This information can be used to enhance the blood bank’s immunisation programme, by deriving individualized immunization policies in which boostering is adjusted to the anticipated anti-RhD decline, effectiveness of boostering and titer levels required.

[Spontaneous antepartal RhD alloimmunization]

AIM OF THE STUDY

Assess the incidence of spontaneous antepartal RhD alloimmunization in RhD negative pregnant women with an RhD positive fetus.

DESIGN

Clinical study.

SETTING

Department of Obstetrics and Gynecology, Medical School and University Hospital Olomouc.

METHODS

A total of 906 RhD negative women with an RhD positive fetus and without the presence of anti-Dalloantibodies at the beginning of pregnancy were examined. Always it was a singleton pregnancy, RhD blood group of the pregnant women was assessed in the 1st trimester of pregnancy, RhD status of the fetus was determined after delivery. Screening for irregular antierythrocyte antibodies was performed in all women in the 1st trimester of pregnancy, at 28-32 weeks gestation and immediately prior to delivery at 38-42 weeks gestation. Screening for irregular antierythrocyte antibodies was performed also at 6 months following delivery in all cases of positive antibodies before delivery. Antibody screening was performed using the indirect antiglobulin (LISS/NAT) and enzyme (papain) test with their subsequent identification using a panel of reference erythrocytes by column agglutination method Dia-Med. After delivery, the volume of fetomaternal hemorrhage was assesed in all RhD negative women and RhD alloimmunization prophylaxis was performed by administering the necessary IgG anti-D dose; none of the women were administered IgG anti-D antepartally.

RESULTS

During screening for irregular antierythrocyte antibodies at 28-32 weeks gestation, anti-D alloantibodies were diagnosed in 0.2% of the women (2/906); immediately prior to the delivery at 38-42 weeks gestation, anti-D alloantibodies were diagnosed in 2.3% of the women (21/906) and repeatedly even at 6 months following delivery (21/157). In 82.7% of the women (749/906), examination at 6 months following delivery was not performed, therefore in these women spontaneous antepartal RhD alloimmunization cannot reliably be ruled out. Alloimmunization may not be diagnosed yet at term of delivery. If anti-D alloantibodies were not present prior to the delivery, these women were all administered IgG anti-D in a dose of at least 125 μg after delivery.

CONCLUSION

In RhD negative women with an RhD positive fetus, the incidence of spontaneous antepartal RhD alloimmunization was at least 2.3%. Most cases may theoretically be prevented by prophylactic administration of 250 μg of IgG anti-D to all RhD negative women at 28 weeks gestation.

Blocked D phenomenon and relevance of maternal serologic testing

A blood requisition for double-volume exchange transfusion was received for a 2-day-old male child born to a 29-year-old multiparous female (P2002) referred to our institute having neonatal jaundice with encephalopathy; no maternal sample was received. the neonatal blood sample was typed as group A, D-, and the direct antiglobulin test (DAT) was strongly positive (4+) using the gel method. Mono-specific DAT showed the presence of IgG antibodies on neonatal red blood cells (RBCs). Acid elution and gentle heat elution (at 56°C) confirmed the presence of anti-D on neonatal RBCs. The baby received two exchange transfusions with group O, D-, packed RBCs compatible with his own serum. Later, on day 3, the neonate's mother was typed as group AB, D-, and her serum revealed the presence of alloanti-D, -C, and -S reactive in the anti-human globulin phase. The anti-D titer was 1024. this report highlights the "blocking" phenomenon caused by maternal anti-D in a case of hemolytic disease of fetus and newborn with a positive DAT.

[Continuous medical evaluation of the prevention of fetomaternal rhesus-D allo-immunization]

OBJECTIVES

To evaluate the prevention of fetomaternal rhesus-D allo-immunization between 2008 and 2010. This evaluation was a part of the continuous medical evaluation (CME) that is compulsory in French hospitals. It was carried out using the tools recommended by the Haute Autorité de santé. We followed the national guidelines for the prevention of fetomaternal rhesus-D allo-immunization as outlined in 2005 by the national French college of Obstetrics and Gynecology.

MATERIALS AND METHODS

We audited 3926 consultations in the first four months of 2008. Based on the results of the audit, actions were implemented to improve care. In 2009, we audited 4021 consultations to look for improvement, and another 3932 consultations in 2010.

RESULTS

In 2008, 14% of the patients had an overall optimal prevention. After actions were taken, 44% of patients in 2009 and 58% of patients in 2010 demonstrated optimal prevention (P<0,05). Especially, the prevention of fetomaternal allo-immunization has been explained for 43% of the patients in 2008 and to 90% of them in 2010. And immunoprophylaxia has been prescribed to 70% of the patients in 2008 and to 93% of them in 2010.

CONCLUSION

This CME has resulted in a statistically significant improvement of the prevention of allo-immunization.

[High-throughput genotyping multiplex ligation-dependent probe amplification for assisting diagnosis in a case of anti-Di(a)-induced severe hemolytic disease of the newborn]

OBJECTIVE

To report a rare case of hemolytic disease of the newborn (HDN) with kernicterus caused by anti-Di(a) diagnosed using high-throughput genotyping multiplex ligation-dependent probe amplification (MLPA).

METHODS

Conventional serological methods were used to detect the antibodies related with HDN. The genotypes of more than 40 red blood cell antigens for the newborn and her parents were obtained using the high-throughput MLPA assay. The antibody titers were tested using a standard serological method.

RESULTS

The unknown antibody against the low-frequency antigens was predicted based on the primary serological tests. The genotyping results for more than 40 red blood cell antigens of the newborn and her parents showed incompatible antigens of MNS and Diego blood group system, indicating the existence of anti-N or anti-Di(a). Further serological tests confirmed anti-Di(a) existence in the plasma of the newborn and her mother. The titer of anti-Di(a) in the mother's plasma was 1:32.

CONCLUSION

Severe HDN including kernicterus can result from anti-Di(a). High-throughput genotyping MLPA assay can help type some rare antigens in complicated cases. The reagent red cell panels including Di(a)-positive cells are necessary in routine antibody screening test in Chinese population.

[Hemolytic disease of the newborn has not vanished from Finland--routine protection of RhD negative mothers during pregnancy is justifiable]

Prophylaxis of RhD negative mothers with anti-D immunoglobulin after childbirth is the most important procedure reducing the immunization of the mother and the risk of severe hemolytic disease of the newborn. In spite of this, anti-D antibodies having relevance to pregnancy are later detected in 1.8% of RhD negative mothers. Half of these cases could be prevented by routine anti-D prophylaxis given to the mothers during weeks 28 to 34 of pregnancy. Convincing evidence of the effectiveness of this measure has accumulated in the last few years, and application of the treatment is justified also in Finland.

The use of anti-D immunoglobulins for rhesus prophylaxis: audit on knowledge and practices among obstetricians

INTRODUCTION

The development of anti-D antibodies results from foetomaternal sensitisation occurring in rhesus (Rh) negative blood group women who carry an Rh-positive foetus. Despite guidelines on Rh immunoprophylaxis, isoimmunisation continues to occur, suggesting that the guidelines are not being fully applied by obstetricians. This study aims to establish the adequacy of knowledge on Rh immunoprophylaxis among obstetricians and trainees in obstetrics and gynaecology in Singapore, and their usual practice in the care of an Rh-negative mother; and hence to audit their practice in accordance with evidence-based guidelines.

METHODS

An anonymous questionnaire survey auditing obstetricians' knowledge of guidelines on anti-D prophylaxis and their usual practice in the clinical setting.

RESULTS

The mean score achieved on the questionnaire was 75.9 percent. Many obstetricians did not know that anti-D immunoglobulins (Ig) should be given within 72 hours of a sensitising event for successful immunoprophylaxis. In clinical practice, all the obstetricians who participated in the questionnaire would offer anti-D Ig prophylaxis to Rh-negative women both antenatally and postnatally. However, only 12.7 percent of them would routinely perform a Kleihauer test in Rh-negative women following delivery.

CONCLUSION

The knowledge on anti-D prophylaxis among obstetricians can be improved. A continual system of education to raise awareness of evidence-based practices as well as clinical audit has been implemented to address this.

Immunologic basis and immunoprophylaxis of RhD induced hemolytic disease of the newborn (HDN)

RhD antigen is the most immunogenic and clinically significant antigen of red blood cells after ABO system. It has historically been associated with hemolytic disease of the newborn (HDN) which is now routinely prevented by the administration of polyclonal anti-D immunoglobulin. This management of HDN has proven to be one of the most successful cases of prophylactic treatment based on antibody mediated immune suppression (AMIS). Despite the increasing efficiency of treatment, the mechanism of action of anti-D is not completely defined. There is a widespread interest in obtaining a reliable therapeutic monoclonal anti-D, due to difficulty of maintaining a pool of high titer volunteer donors for plasma collection and also increasing demand for antenatal prophylaxis and safety issues with plasma derived products. Candidate monoclonal anti-D preparations should demonstrate appropriate functionality in both in vitro and in vivo assays comparable to polyclonal anti-D immunoglobulin. These criteria are reviewed in addition to the factors regulating development of D specific immune response in D negative individuals and its suppression in HDN prophylaxis.

Epitope specificity and isotype of monoclonal anti-D antibodies dictate their ability to inhibit phagocytosis of opsonized platelets

Rh immune globulin (WinRho SDF; Cangene, Mississauga, ON, Canada) is an effective treatment for autoimmune thrombocytopenic purpura; however, maintaining a sustained supply for its use in autoimmune thrombocytopenic purpura and its primary indication, hemolytic disease of the newborn, makes the development of alternative reagents desirable. We compared Rh immune globulin and 6 human monoclonal anti-D antibodies (MoAnti-D) with differing isotypes and specificities for their ability to opsonize erythrocytes and inhibit platelet phagocytosis in an in vitro assay. Results demonstrated that opsonization of erythrocytes with Rh immune globulin significantly (P < .001) reduced phagocytosis of fluorescently labeled opsonized platelets in an Fc-dependent manner. Of the MoAnti-D that shared specificity but differed in isotype, only IgG3 antibodies could significantly (P < .001) inhibit platelet phagocytosis. In contrast, 2 MoAnti-D shared isotypes and differed in specificity; however, only one could significantly (P < .001) inhibit platelet phagocytosis. The results suggest that MoAnti-D epitope specificity and isotypes are critical requirements for optimal inhibition of opsonized platelet phagocytosis.

Thrombocytopenia associated with dengue hemorrhagic fever responds to intravenous administration of anti-D (Rh(0)-D) immune globulin

Severe thrombocytopenia and increased vascular permeability are two major characteristics of dengue hemorrhagic fever (DHF). An immune mechanism of thrombocytopenia due to increased platelet destruction appears to be operative in patients with DHF (see Saito et al., 2004, Clin Exp Immunol 138: 299-303; Mitrakul, 1979, Am J Trop Med Hyg 26: 975-984; and Boonpucknavig, 1979, Am J Trop Med Hyg 28: 881-884). The interim data of two randomized placebo controlled trials in patients (N = 47) meeting WHO criteria for dengue hemorrhagic fever (DHF) with severe thrombocytopenia (platelets < or = 50,000/mm(3)) reveal that the increase in platelet count with anti-D immune globulin (WinRho SDF), 50 microg/kg (250 IU/kg) intravenously is more brisk than the placebo group. The mean maximum platelet count of the anti-D-treated group at 48 hours was 91,500/mm(3) compared with 69,333/mm(3) in the placebo group. 75% of the anti-D-treated group demonstrated an increase of platelet counts > or = 20,000 compared with only 58% in the placebo group. These data suggest that treatment of severe thrombocytopenia accompanying DHF with anti-D may be a useful and safe therapeutic option.

Lymphocyte antibody-dependent cytotoxicity test for evaluation of clinical role of monoclonal anti-D-antibodies for prevention of rhesus sensitization

Monoclonal antibodies to D antigen were studied in the reaction of antibody-dependent cytotoxicity for evaluation of the possibility of using these antibodies for preventing rhesus sensitization. High hemolytic activity of four anti-D-monoclonal antibodies in the antibody-dependent cytotoxicity test, mediated by their interaction with FcgammaRI, and the capacity to accelerate elimination of D+ erythrocytes from circulation did not provide the immunosuppressive effect. It was hypothesized that monoclonal antibodies for prevention of rhesus sensitization should interact with FcgammaRIII on lymphocytes. These monoclonal antibodies are extremely rare: only 4 of 125 studied antibodies mediated hemolysis in the antibody-dependent cytotoxicity test with lymphocytes, while all polyclonal anti-D-preparations exhibited this activity.

The analysis and quantification of a clonal B cell response in a hyperimmunized anti-D donor

Healthy volunteers are hyperimmunized with RhD-positive red cells in order to obtain plasma containing high titres of anti-D immunoglobulin, which is used for the prevention of haemolytic disease of the fetus and newborn. We analysed the anti-D immune response in a donor who had been hyperimmunized for 7 years and who showed declining anti-D titres despite re-immunization. A phage display library representing the complete immunorepertoire and a second library representing the IGHV3 superspecies family genes (IGHV3s) repertoire in the donor were constructed and analysed. A clonal Ig-gene rearrangement was quantified in the peripheral blood by limiting dilution polymerase chain reaction (PCR) All RhD-binding phages from both libraries, except one, had heavy chains with IGH-VDJ rearrangements of the same clonal origin, but with different patterns of somatic mutations and joined with different light chains. Limiting dilution PCR performed on mRNA and genomic DNA showed a frequency of 1 clonal B cell in 2000 IgG1/3-positive B cells. We show the presence of clonally related RhD-specific B cells in a hyperimmunized anti-D donor who had declining anti-D titres and who was unresponsive to re-immunization. Furthermore, we found a high frequency of clonal B cells. These results contribute to the understanding of the immune response against RhD in hyperimmunized anti-D donors.

In vitro functional test of two subclasses of an anti-RhD antibody produced by transient expression in COS cells

For over 35 years hemolytic disease of the fetus and newborn (HDFN) due to RhD has been effectively prevented by anti-RhD antibodies obtained from alloimmunized women or deliberately immunized men. However, due to the reduced number of immunized women and for ethical reasons it is foreseen that other sources of anti-RhD will be needed. One such source is recombinant human antibodies. Here we describe the construction of plasmids encoding two subclasses (IgG1 and IgG3) of an anti-RhD antibody, their transient expression in COS cells, and subsequent functional characterization of the antibodies with regard to specificity and ability to mediate a respiratory burst. The recombinant anti-RhD antibodies were specific for the RhD antigen and were able to mediate a respiratory burst. Thus these antibodies might be of use as future rhesus prophylaxis.

[Adverse effects and patient information]

Anti-D prophylaxis should be proposed to all RhD negative non-sensitized pregnant women, after delivering an information concerning both Rhesus disease and anti-D immunoglobulins. This information must be delivered as a written document and the patient's oral consent is required before administration of the anti-D immunoglobulins. Anti-D immunoglobulins currently used in France for prophylaxis are extracted from plasma of hyperimmunized paid donors. Even if all the conditions of viral safety are fulfilled in the preparation of anti-D immunoglobulins, they remain blood derived products. As such, prescription of anti-D immunoglobulins should follow legal rules concerning tracability and information. Refusal of rhesus prophylaxis can occur but should be transcribed and motivated in the patient's chart. Administration of anti-D immunoglobulins is usually well tolerated. Reactions to hemolysis of fetal Rhesus positive red cells can occur but remain rare and linked to important foeto-maternal hemorrhage. They can be easily prevented or treated by anti-inflammatory drugs. Patients can be vaccinated against rubella in the post-partum period even though they will receive a concomitant prophylaxis with Rh immunoglobulin. Persistence of passive anti-D in maternal circulation after injection lasts several weeks or months and could have various consequences. In the mother: it can interfere with diagnosis of active anti-D immunization. In most cases, it may be possible to differentiate passive and immune anti-D. When reliable information concerning date and dosage of antenatal anti-D prophylaxis are available. In the newborn: anti-D immunoglobulins can pass through the placenta and enter the fetal circulation, coat the D positive fetal red cells and give positive DAT. Positive DAT is reported in 5 to 15% of the newborns following rhesus prophylaxis in the third trimester but with no report of anemia or jaundice. In absence of ABO incompatibility, no additional investigation is needed in these newborns.

[Prevention of fetomaternal rhesus-D allo-immunization. Perspectives]

At present, rhesus prophylaxis concerns RhD negative pregnant women, even though 30 to 40% of them are bearing a RhD negative child. Knowing the RhD fetal genotype could change this quite irrational practice of prophylaxis (exposing many more women than needed to blood derived products) without reducing its efficacy. RhD fetal genotype determined on amniotic fluid has an excellent sensitivity. Presence of silent D genes slightly impairs its specificity which remains acceptable. However women have to be informed of possible false positives. Fetal RhD genotyping on maternal blood is more complex. Sensitivity is good from 10 GW and excellent after 15 GW. In case of a first negative result, it is recommended to control fetal RhD on a second sample drawn a few weeks later. Another new perspective for rhesus prophylaxis is the attempt to substitute polyclonal IgG anti-D into human monoclonal IgG anti-D. The main difficulty is to elaborate monoclonal antibodies with a capacity to neutralize RhD positive red blood cells equivalent to those of polyclonal anti-D. A new generation of antibodies is in process and preliminary clinical results are suggesting a possible use of these monoclonal antibodies for future rhesus prophylaxis but long-term follow-up is required to draw further conclusions.

[Prevention of fetomaternal rhesus-D allo-immunization. Practical aspects]

RhD prophylaxis concerns RhD negative women, who are non-sensitized against D antigen during and at the end of their pregnancy with a RhD positive child. RhD prophylaxis includes targeted prophylaxis (prevention of anti-D immunization after feto-maternal hemorrhage (FMH) induced by prenatal events and delivery) and routine antenatal D prophylaxis (prevention of anti-D immunization resulting from spontaneous FMH in the last trimester of pregnancy). Targeted prophylaxis should be applied regardless of the gestational age and a dose of 100microg anti-D is usually enough (200microg is the lowest dosage currently available in France). However it is recommended to quantify the volume of feto-maternal hemorrhage to avoid administration of a dose of IgG anti-D less than 20microg per ml of fetal red blood cells. Efficacy of prophylaxis relies also on the delay between the sensitizing event and the injection of anti-D, delay should be less than 72 hours. Intravenous administration of anti-D allows immediate neutralization of D positive fetal red blood cells and should be, if possible, preferred to intramuscular administration (IM). After a first injection of anti-D, if repetition of potential sensitizing events occurs, abstention of prophylaxis is possible depending on the previous administrated dose (protection lasts 6 weeks for 200microg and 9 weeks for 300microg) and the amount of feto-maternal hemorrhage. For routine prophylaxis of the third trimester, 300microg of anti-D should be proposed IM at 281+/-GW. Abstention of Rh prophylaxis is possible if the alleged father is certified RhD negative or if the fetal RhD genotype is confirmed negative. At delivery, RhD phenotype of the newborn should be determined even if RhD fetal genotype is known. Maternal blood should be drawn for quantification of feto-maternal transfusion at least 30 min after delivery is completed.

Immune complexes as therapy for autoimmunity

For several decades, intravenous Ig has been used as treatment for a variety of immune-related diseases, including immune thrombocytopenic purpura (ITP), autoimmune neuropathies, systemic lupus erythematosus, myasthenia gravis, Guillain-Barré syndrome, skin blistering syndromes, and Kawasaki disease. Despite years of use, its mechanism of immunomodulation is still unclear. Recent studies using mouse models of ITP and arthritis, including one reported in this issue of the JCI, now provide some insights into this mechanism and the rationale for the development of Fcgamma receptor-targeted therapeutics.

Red blood cell iso-immunisation in the Wellington area of New Zealand: the case for antenatal prophylaxis

The present study aimed to calculate the rate of Rhesus D iso-immunisation during pregnancy in Wellington, New Zealand and to identify the timing of iso-immunisation. The notes of all women and their babies with positive antenatal anti-D antibody screens during the period 1994-2002 at the regional reference laboratory (Wellington Blood Transfusion Service) were reviewed to identify the antibody titre and the stage of pregnancy that the antibodies developed. Twelve percent of all tested pregnant women were Rhesus D negative and the annual immunisation rate during pregnancy was 1.4%. Sensitisation during the third trimester occurred in 50% of these women. Sensitisation in the third trimester was more common in primigravid women (87%) than in multiparous women (27%).

Platelet transfusion in an infant leading to formation of anti-D: implications for immunoprophylaxis

BACKGROUND

The immature infant immune system rarely makes RBC alloantibodies; however, most studies confirming the absence of alloantibodies in infants have involved transfusions that were matched for one of the most immunogenic antigens, rhesus D. The potential for D- infants to develop anti-D is unknown. Specifically, this issue has not been analyzed for infants receiving whole-blood-derived PLTs from D+ donors. The importance of understanding such risk is underscored by the fact that anti-D formation can be prevented by the administration of Rh immunoglobulin.

CASE REPORT

A D- infant with congenital heart disease received two D-mismatched whole-blood-derived PLT units at 17 weeks of age. He did not receive Rh immunoglobulin prophylaxis. Upon a subsequent admission 13 months later, anti-D was identified in his plasma sample.

CONCLUSION

The case presented here demonstrates that a young infant can respond to less than 0.6 mL of D+ RBCs and documents the youngest patient to have developed a RBC alloantibody from a PLT transfusion. To prevent anti-D formation, we recommend administering Rh immunoglobulin to all D- pediatric patients that receive PLT transfusions from D+ donors [correction].

Indications of neutralising anti-idiotypic antibodies and selective proteolytic fragmentation in polyclonal anti-D IgG preparations

Proteolytic fragmentation is the only suggested cause of potency losses during storage of liquid human polyclonal anti-D Ig. Besides the effect of fragmentation, we have investigated the potential contribution of neutralising anti-idiotypic antibodies (anti-Ids). Potency changes during storage and/or upon pH reduction in anti-D IgG batches with or without addition of plasminogen and urokinase were quantitatively analysed by the autoanalyser (AA) method or by a special procedure of flow cytometry (FC). Moreover, simultaneous changes of the molecular size distribution pattern have been determined by size exclusion chromatography. In contrast to the AA procedure, the particular FC methodology was found to be almost insensitive to proteolysis comprising up to 30% of total IgG. Data interpretation was based on the assumption that both assays cannot detect Ids with neutralised paratopes. In the absence of detectable neutralisation (functional absence of anti-Ids), it could be demonstrated that the anti-D IgG subpopulation is more sensitive to fragmentation by endogenous protease as compared to the unrelated bulk. However, both methods detected batch- and assay-dependently variable potency losses during storage. Moreover, the increase of potency induced by pH reduction correlated with the increase of monomeric IgG, essentially on the expense of dimers. This finding was interpreted to indirectly indicate the neutralising action of anti-Ids known to be the major driving force of dimer formation in polyclonal IgG. A more or less pronounced pH-dependent potency increase was also detectable in three arbitrarily selected batches of two other manufacturers. The data allows to assume that anti-Id-mediated neutralisation can significantly contribute to losses of anti-D potency. In addition, it turned out that anti-D plasma itself can be the source of anti-Ids.

Clearance of red cells by monoclonal IgG3 anti-D in vivo is affected by the VF polymorphism of Fcgamma RIIIa (CD16)

Human red cells (RBC) coated with IgG anti-D are cleared from the circulation to the spleen by macrophages which express IgG receptors (Fcgamma R). Polymorphisms of Fcgamma RIIa and Fcgamma RIIIa affect IgG binding in vitro, and may alter the efficiency of clearance of immune complexes in vivo. In a RBC clearance study, 22 Rh D-negative subjects were given 100-400 micro g human monoclonal or polyclonal IgG anti-D i.m. followed 48 h later by 51Cr-labelled D+ RBC. The half lives of the infused D+ RBC were determined, together with the coating levels of anti-D on the D+ RBC. Fcgamma RIIA and FcgammaRIIIA genotyping was performed. Large ranges of phagocytosis and extracellular lysis of RBC in vitro, and of half lives of RBC in vivo, were observed. Clearance of RBC coated with monoclonal IgG3 anti-D (BRAD-3) was more rapid in five subjects homozygous for Fcgamma RIIIa-F/F158 than in three subjects expressing the Fcgamma RIIIa-V158 allele (P = 0.024). This effect was not observed, however, for those individuals given polyclonal anti-D. There was also no significant difference in the efficiency of RBC destruction in vitro or of RBC clearance in vivo between the subjects analysed for individual genotypes or alleles or combinations of alleles. In conclusion, the presence of the Fcgamma RIIIa-V158 allele compromised the efficiency of removal of RBC coated with IgG3 anti-D.

Fc receptor blockade in patients with refractory chronic immune thrombocytopenic purpura with anti-D IgG

BACKGROUND

This is an evaluation of the treatment of 63 patients with chronic immune thrombocytopenic purpura (54 splenectomized and nine nonsplenectomized) with weekly doses of anti-D (IgG)-coated red blood cells (RBCs).

METHODS

All patients were given one 5-15 microg/kg/dose of intravenous (i.v.) anti-D (IgG)-coated RBCs per week (average of 300 microg/dose/week) for a median 3-month period (3-6 months). Treatment modality was evaluated on a weekly basis by platelet counts, measuring of hemoglobin levels, and performance of Coombs tests.

RESULTS

All patients presented a clinical response. Fifty-two patients (82.5%) increased their platelet count (PC) and 45 (69.8%) increased their PC >50 x 10(9)/L. In 34 cases, response was sustained. Six of nine nonsplenectomized patients (67%) increased PC, thus avoiding splenectomy; four patients attained a stable complete response (CR). Similar platelet responses were observed in homozygous and heterozygous Rh (D)-positive patients (Rh/Hr phenotypes). Currently, after >10 years, 43 patients present a now permanent complete response with platelet count >50 x 10(9)/L. Ten patients subsequently decreased their platelet count, although they were able to attain CR after receiving six doses of anti-D (IgG)-coated RBCs.

CONCLUSIONS

Based on our study of Fc receptor blockade treatment with anti-D (IgG)-coated RBCs with the most difficult cases of ITP, which resulted in a 69.8% successful response rate, we concluded that weekly prescription of anti-D (IgG)-coated RBCs is an effective approach to treating chronic refractory ITP.

Perinatal immunomodulation

The fetus and the neonate are particularly vulnerable to injury caused directly by immunologic mechanisms or inflicted by infectious agents that take advantage of their relatively immature and inexperienced immune system. With increasing survival of high-risk neonates in the surfactant era, prevention/treatment of sepsis and chronic lung disease (CLD) has emerged as an area of priority in neonatal research. Considering the role of inflammatory mediators in the pathogenesis of sepsis and CLD, the clinical application of immunomodulator therapy to neonatology is perhaps more important at present than ever. Advances in molecular biology and immunology have led to development of newer immune modulator therapies that are directed towards specific cells or cytokines rather than resulting in a general suppression of the immune response. Failure of promising, newer immunomodulator therapies in sepsis trials in adults has, however, clearly documented the difficulties in diagnosing/correcting the imbalance between pro- and anti-inflammatory responses. As in the case of sepsis, development of a single magic bullet for prevention/management of a multi-factorial illness like CLD may be difficult, as prevention of prematurity - the single most important high-risk factor for CLD - is an unachievable goal at present. As new frontiers are being explored, older, well-established therapies like antenatal anti-D immunoglobulin prophylaxis continue to emphasize the tremendous potential of immunomodulator therapy in neonatology/perinatology. The current immunomodulators/immunotherapeutic agents with established/potential clinical applications in the perinatal period are reviewed.

Intravenous Rh immune globulin for treating immune thrombocytopenic purpura

Intravenous Rh [corrected] immune globulin was licensed by the U. S. Food and Drug administration in 1995 for the treatment of acute and chronic immune thrombocytopenic purpura in children and chronic immune thrombocytopenic purpura in adults. In 1996, the American Society of Hematology published a practice guideline for immune thrombocytopenic purpura, but treatment recommendations of necessity were formulated using only results of early clinical trials with intravenous Rh immune globulin. To date, there are no published results of large-scale clinical trials comparing conventional doses of intravenous immune globulin with the most promising dose range for intravenous Rh immune globulin (50-75 microg/kg). However, clinical experience is accumulating to indicate that intravenous Rh immune globulin is as effective, probably safer, and easier to administer than intravenous immune globulin. Acute intravascular hemolysis after infusions of intravenous Rh immune globulin for immune thrombocytopenic purpura has been reported with an estimated incidence of 1 in 1,115 patients. The risk factors for this adverse event have not been defined.

RhD isoimmunization and current management modalities

OBJECTIVE

To review the literature on current perspectives and treatment of RhD isoimmunization.

DATA SOURCES

A search was conducted on MEDLINE and CINAHL, and supplemental articles/ bulletins were obtained from cited references and the Web site of the American College of Obstetricians and Gynecologists. Recent texts also were reviewed. Key search words: isoimmunization, Rho (d) immune globulin, fetal erythroblastosis, intrauterine blood transfusions, alloimmunization.

STUDY SELECTION

Articles and comprehensive works from indexed journals in the English language relevant to key words and published after 1995 were evaluated. Historically relevant periodicals and texts were also reviewed and selected.

DATA EXTRACTION

Data were extracted and organized under the following headings: testing of the antepartum patient, antepartum treatment of isoimmunization, testing of the postpartum patient, anti-D immune globulin, antepartum anti-D immune globulin prophylaxis, other antepartum and obstetric indications for anti-D immune globulin administration, postpartum anti-D immune globulin prophylaxis, nursing implications, and future possibilities.

DATA SYNTHESIS

RhD isoimmunized pregnancies continue to contribute to worldwide perinatal and neonatal morbidity and mortality. This review describes the basic knowledge necessary to care for these pregnancies and the current management modalities.

CONCLUSIONS

The management options for RhD compromised gestations continue to evolve almost as quickly as technological advances are made. Multiple areas of research in this field have surfaced, and nurses can become valuable members of these research teams. The literature also indicates that with the available knowledge and resources, the current rate of RhD isoimmunization can be further decreased with closer adherence to proposed management guidelines by all health care professionals.

Clinical value of an antibody-dependent cell-mediated cytotoxicity assay in the management of Rh D alloimmunization

OBJECTIVE

The aim of this study was to evaluate the clinical value of an antibody-dependent cell-mediated cytotoxicity assay relative to the indirect antiglobulin test titer in the management of Rh D-alloimmunized pregnancies.

STUDY DESIGN

Data from 172 Rh D-alloimmunized pregnancies were analyzed retrospectively. The accuracies of the highest antibody titer and of the highest antibody-dependent cell-mediated cytotoxicity assay result during pregnancy to predict fetal and neonatal Rh disease, defined as the need for intrauterine (n = 30) or neonatal (n = 37) blood transfusion, respectively, were assessed.

RESULTS

At different cutoff levels with equal sensitivities the antibody-dependent cell-mediated cytotoxicity assay consistently showed a higher specificity than the antibody titer for the prediction of fetal disease. No difference was found between the receiver operating characteristic curves of the 2 tests for the prediction of neonatal disease.

CONCLUSIONS

Selection of patients for referral and invasive testing for Rh D alloimmunization may be improved with the use of an antibody-dependent cell-mediated cytotoxicity assay.

The first example of a paraben-dependent antibody to an Rh protein

BACKGROUND

Parabens are added to a commercial LISS (C-LISS) to retard microbial growth. Paraben-dependent anti-Jk(a) has been detected by the use of C-LISS.

CASE REPORT

Serum from a D+ woman reacted in antiglobulin tests with RBCs stored (2-4 hours, 22-25 degrees C) in C-LISS (Löw and Messeter formulation, Immucor). Freshly prepared C-LISS-suspended RBCs did not react; nor did RBCs stored in LISS-additive reagents, PEG, saline, or homemade LISS.

RESULTS

Studies using C-LISS-stored RBCs revealed an antibody that reacted with D+ and rrV+ RBCs, but not with r'r, r"r, or rrV-VS- RBCs. All partial D RBC phenotypes tested reacted, as did D+LW-, rGr, r"Gr, r(y)r, r'(s)rV+VS+, and r'(s)rV-VS+ RBCs. The active ingredient in C-LISS was propylparaben. Other LISS ingredients were not required; saline solutions of propylparaben, ethylparaben, methyl salicylate, 2-phenoxyethanol, and butylparaben were active. Methylparaben and methyl-m-hydroxybenzoate were inactive. Reactivity to C-LISS-stored RBCs could not be inhibited by propylparaben. Reactivity with D+V- and D-V+VS+ RBCs was not separable by adsorption-elution.

CONCLUSIONS

This antibody likely detects a neoantigen formed between active compounds and RBC membranes. Review of the structure of active compounds suggests that proximity between methyl and hydroxyl groups is important for binding with RBC membranes. The role of RhD is unclear; no single portion of RhD protein appears to be implicated.

Towards a quantitative model of immunogenicity: counting pathways in sequence space

One of the fundamental aims of structural biology is the identification of high-affinity ligands for arbitrary receptors. The maturation of the antibody repertoire elegantly and robustly solves this problem through an evolutionary mechanism comprising repeated cycles of mutation and preferential replication. To understand better the limitations and biases of this process, we developed an interpretation of antibody maturation within the framework of sequence space and fitness landscapes. Several well-described phenomena can be directly derived from this framework, and new predictions can be made. Ultimately, this reconceptualization of the clonal selection process suggests a quantitative, testable model of immunogenicity.

Sequence and specificity analysis of recombinant human Fab anti-Rh D isolated by phage display

BACKGROUND AND OBJECTIVES

Hyperimmune anti-Rh D serum is worldwide in short supply. As a first step to develop an alternative source of Rh D antibodies, we describe in this study the isolation and characterization of recombinant anti-Rh D Fab fragments.

MATERIALS AND METHODS

Peripheral blood mononuclear cells harvested from a hyperimmunized donor were used to construct two combinatorial Fab libraries. Phages expressing these Fab fragments were selected on whole red blood cells followed by testing of positive clones in an indirect hemagglutination assay.

RESULTS

Individual Fab clones are of high affinity and competitively inhibit the binding of a registered anti-D immunoglobulin. The Fab clones are also specific against the partial D phenotypes, Rh33, DIII, DIVa, DIVb, DVa, and DVII. The 13 different but highly homologous clones express preferentially VH3 segments.

CONCLUSION

These Fab fragments show potential for the development of a new generation of therapeutic anti-Rh D reagents.

A stable reagent system for screening and identifying red blood cell irregular antibodies: application to commercial antibodies

OBJECTIVE

Development of a new solid-phase system for screening and identifying irregular red cell antibodies.

MATERIALS AND METHODS

Red blood cell membranes were prepared by a semi-automated procedure in which the hemolysate solution was passed through a hollow-fiber system. The membranes were fixed to the solid phase (microtiter plates) by centrifugation and incubated with 8% fat-free milk. Antibodies added to the microtiter plate were detected by anti-human antibodies adsorbed onto yellow latex particles.

RESULTS

The system had good sensitivity (titer <1); 97% of anti-D samples were detected. The detection system was stable for 6 months at 4 degrees C.

CONCLUSION

This stable-antigen solid-phase system readily detects and identifies red cell antibodies that are important in transfusion.

False-positive eluate reactivity due to the low-ionic wash solution used with commercial acid-elution kits

BACKGROUND

During the use of commercial red cell (RBC) acid-elution kits for adsorption and elution (adsorption/elution) studies with anti-D, unexpected reactive eluates (anti-D) were obtained from D- RBCs. Such results were not obtained with a parallel xylene method or, historically, with heat and ether methods.

STUDY DESIGN AND METHODS

Single-donor and commercial polyclonal anti-D samples were incubated with D+ and D- RBCs. Acid eluates were prepared by the manufacturers' directions. Variations in the wash step of the eluate preparation included the use of commercial kit wash solution versus phosphate-buffered saline versus solutions of various ionic strengths.

RESULTS

Anti-D was eluted from 20 of 22 samples of D- RBCs after incubation with commercial polyclonal anti-D (titer 512) and from 2 of 3 samples of D- RBCs incubated with single-donor anti-D (titer 256). With a low-titer (16) single-donor anti-D, 0 of 4 eluates from D- RBCs reacted. When phosphate-buffered saline was substituted for the commercial wash solution, 0 of 11 D- RBC eluates reacted, as compared with 9 of 11 D- RBCs that yielded positive 1+(-)2+ eluates with the commercial wash solution. If the recommended initial phosphate-buffered saline wash was omitted before the use of the commercial wash solution, the eluate reactivity was stronger (2+(-)3+). When low-ionic-strength (< 0.03 M) saline was substituted, anti-D was eluted from D- RBCs. All last washes were nonreactive. Antiglobulin tests on all adsorbing D- were negative.

CONCLUSION

Commercial wash solutions used for acid elution are at low ionic strength and commonly yield superior eluates, but in the presence of high-titer antibodies, false-positive eluates can result. It is our belief that the low-ionic-strength wash solution caused aggregation of IgG and nonspecific attachment of IgG on RBCs. Aggregates will contain IgG serum antibodies in proportion to the titer of the antibody. It is this nonspecifically bound antibody that is eluted from antigen-negative RBCs.

Anti-D: mechanisms of action

Immunoglobulin that recognizes and binds specifically to the erythrocyte D antigen (anti-D globulin, WinRho SDF; Nabi, Boca Raton, FL) has recently been shown to be an effective therapy for many patients with idiopathic thrombocytopenic purpura (ITP). Its mechanisms of action are not completely understood. Intravenous (IV) infusion of anti-D into a D-positive recipient leads to antibody coating of circulating erythrocytes that are cleared primarily by the spleen. This immune-mediated clearance of sensitized erythrocytes occupies the reticuloendothelial system and allows survival of antibody-coated platelets. Based on clinical observations, experimental data, and theoretical calculations, the efficacy of anti-D therapy in ITP depends on several factors that influence the amount of erythrocyte sensitization and the rate of immune-mediated erythrocyte clearance by the spleen. Antibody characteristics, including the antibody concentration, binding affinity, and dissociation constants, may be important, as well as the number of D-antigen binding sites on the erythrocytes. Although the primary mechanism of action of anti-D is believed to be immunologic blockade of Fc receptors (FcR) within the reticuloendothelial system (RES), other immunomodulatory effects are also possible.

Cold agglutinin activity is common among human monoclonal IgM Rh system antibodies using the V4-34 heavy chain variable gene segment

BACKGROUND

The V4-34 gene segment is commonly used by human monoclonal IgM alloantibodies against blood group antigens and by cold-reactive red cell autoantibodies with anti-I or anti-i specificity. This study was conducted to determine whether cold agglutinin activity is found among the V4-34-encoded alloantibodies.

STUDY DESIGN AND METHODS

Fifty-four human IgM monoclonal antibodies (MoAbs) against Rh system antigens were tested for cold agglutinin activity against red cells lacking the relevant Rh system antigen and for reactivity with tissue I and/or i antigens using immunohistochemistry. The findings were correlated with the utilization of the V4-34 segment as determined in an enzyme-linked immunosorbent assay with an antibody (9G4) that is specific for this gene product and were also correlated with other serologic properties.

RESULTS

Of the MoAbs, 59 percent were 9G4-positive. Of the 9G4-positive subset, 16 and 44 percent agglutinated native adult (express I) and cord (express i) cells, respectively, at 4 degrees C; these levels rose to 84 and 94 percent, respectively, with the use of papain-treated cells. The red cell antigens recognized at 4 degrees C were cleaved by endo-beta-galactosidase, which is consistent with their being I and i. Of the 9G4-positive subset, 53 percent bound to tissue i antigen. These reactivities were not found among 9G4-negative MoAbs. Endo-beta-galactosidase treatment of red cells enhanced Rh system antibody agglutination by 9G4-negative MoAbs.

CONCLUSION

Anti-I/i reactivity is common among IgM Rh system MoAbs and is shown only by the V4-34-encoded subset. This finding has implications for the use of MoAbs for Rh system typing of blood.

Interferon-associated thyroid dysfunction in anti-D-related chronic hepatitis C

To assess the frequency and nature of thyroid abnormality in association with interferon (IFN) therapy alone and in combination with ribavirin, 19 patients receiving IFN therapy for hepatitis C virus (HCV)-induced liver disease had thyroid function tests assessed on a monthly basis. Group I (n = 9) patients received 5 million U of IFN s.c. daily for 2 weeks, followed by 3 million U three times per week for 6 months. Group II (n = 10) patients received 3 million U IFN s.c. three times per week together with ribavirin 400 mg twice daily orally for 6 months. Five of 19 patients (26.3%) developed thyroid abnormalities, 3 (33.3%) in group I and 2 (20%) in group II. Three patients developed thyroid function tests consistent with hyperactivity, and 2 of these normalized on cessation of IFN therapy. One patient continued on IFN but remained clinically euthyroid with antithyroid treatment. Two patients developed thyroiditis and required thyroid supplementation. (One of the 2 had pretreatment antimicrosomal thyroid antibodies and a positive family history of thyroid disease.) Of the 3 patients with HCV type 1b, 1 had pretreatment thyroid antibodies, and all 3 had antibodies during IFN therapy. Neither of the 2 patients with genotype 3 had pre-IFN or post-IFN thyroid antibodies. Patients on IFN therapy need regular thyroid function testing. The frequency of abnormal thyroid tests may be dose related. HCV genotype may influence the development of thyroid antibodies.

Antigen topography is critical for interaction of IgG2 anti-red-cell antibodies with Fc gamma receptors

IgG antibodies to the Rh D polypeptide on red cells are normally IgG1 or IgG3, whereas antibodies produced in response to carbohydrate antigens such as the A and B blood groups are predominantly IgG2. The consequences of this isotype restriction for the immune destruction of red cells were investigated. Human IgG2 anti-D and IgG2 anti-A were isolated by affinity purification from an unusual anti-D serum (DEL) and anti-A sera, respectively. These antibodies were compared with IgG1 and IgG3 monoclonal anti-D in in vitro functional assays of the interaction between IgG-coated red cells (EA-IgG) and cells bearing IgG Fc receptors (Fc gamma R). Dimeric IgG2 anti-D bound efficiently to cell lines transfected with Fc gamma RIIa-H131, an allotypic form of Fc gamma RIIa which readily interacts with IgG2, IgG1 and IgG3. Unexpectedly, however, -D- phenotype red cells coated with IgG2 anti-D did not form rosettes with these cells, whereas EA-IgG2 anti-A and EA-IgG1 and EA-IgG3 anti-D effectively formed rosettes with these transfectants at the same sensitization level (100,000 molecules IgG/red cell). In antibody-dependent cell-mediated cytotoxicity (ADCC) assays, lysis of EA-IgG2 anti-A was mediated via Fc gamma RIIa, whereas lysis of EA-IgG1 and EA-IgG3 anti-D was mediated via Fc gamma RI or Fc gamma RIII; EA-IgG2 anti-D was inactive in all functional assays. These experiments suggest that both IgG subclass and antigen structure affect functional IgG-Fc gamma R interactions. The topography of the Rh D antigen, an integral membrane protein, ensures that anti-D is bound near the lipid bilayer surrounded by the glycocalyx. This may sterically hinder access of Fc gamma RIIa-H131 to the Fc gamma R recognition site on the relatively inflexible IgG2 anti-D, but not to that of IgG1 or IgG3 anti-D. In contrast, IgG2 bound to the A antigen on glycoproteins is not so constrained. The topography of the D and A antigens may thus determine whether functional interactions of red-cell-bound IgG2 anti-D and IgG2 anti-A with cells bearing Fc gamma receptors can occur.

Treatment of chronic autoimmune thrombocytopenic purpura with monoclonal anti-D

BACKGROUND

The platelet count increases transiently after treatment with polyclonal anti-D in about 50 percent of D+ patients with autoimmune thrombocytopenic purpura (AITP). The effect is usually attributed to macrophage Fc-receptor blockade by antibody-coated red cells. As polyclonal anti-D is in limited supply, prospective testing was performed on a monoclonal anti-D (MoAb D) in such patients.

STUDY DESIGN AND METHODS

Seven D+ patients with chronic AITP received MoAb D intravenously at doses of 47 to 95 microg per kg of body weight. Response was assessed by studying platelet count increment. Hemolysis and red cell-bound MoAb D were measured before and after MoAb D administration.

RESULTS

MoAb D red cell binding was demonstrated in all patients at a ratio higher than that observed in AITP patients successfully treated with polyclonal anti-D. However, little or no platelet count increment was observed in six patients, while a transient response was observed in only one (platelet count 97 x 10(9)/L before MoAb D infusion and 163 x 10(9)/L 4 days later). Furthermore, because five patients showed signs of hemolysis and two became anemic, higher doses of MoAb D should be used only with caution in patients with AITP.

CONCLUSION

The MoAb D used in this study cannot be proposed as an alternative treatment for patients with AITP.

Urticaria from allergy to a purified human anti-Rh antibody preparation

This case presentation describes a young woman who developed generalized urticaria after receiving the human anti-RhD(D) preparation, WinRho, intravenously. Allergy skin tests and the radioallergosorbent test (RAST) for IgE antibodies to the human anti-D immunoglobulin preparation were positive. Further studies using high-pressure liquid chromatography and protein A column chromatography implicated a nonimmunoglobulin low-molecular-weight contaminant. This case report illustrates an allergic reaction to a highly purified human immunoglobulin preparation, and demonstrates approaches to assessment of such a reaction.

Alloimmunization during pregnancy treated with high dose intravenous immunoglobulin. Effects on fetal hemoglobin concentration and anti-D concentrations in the mother and fetus

BACKGROUND

High dose intravenous immunoglobulin has been reported to be advantageous in the treatment of alloimmunization during pregnancy. The mode of action is unknown.

METHOD

High dose intravenous immunoglobulin was used as the sole prenatal treatment in six severely rhesus(D) sensitized pregnant women. Maternal and fetal anti-D concentrations as well as fetal hemoglobin concentrations were studied. Seven pregnancies in rhesus(D) sensitized women served as controls. They received no treatment because they had milder forms of erythroblastosis fetalis or, in one case, a rhesus(D) negative fetus.

RESULT

No obvious inhibitory effect of the treatment on maternal anti-D production and transplacental anti-D passage to the fetus was found. The fetal hemoglobin concentrations remained stable at about 80 g/L (hematocrit 27%) in five of six treated patients while there was a significant decrease in the control group.

CONCLUSION

High dose intravenous immunoglobulin treatment seems to act mainly on fetal red cell destruction rate, possibly by blocking Fc receptor mediated macrophage phagocytosis. We claim that the treatment can successfully be used to prevent further deterioration of fetal anemia in rhesus(D) immunizations if started before severe fetal anemia (hemoglobin concentration < 70 g/L, hematocrit < 23%) and imminent hydrops fetalis arises.

HLA phenotypes and severe Rh(D) immunization

Blood samples from 24 Rh(D) immunized women were analyzed for antibody titers and quantification of anti-D. The HLA-DR and -DQ polymorphisms were identified as RFLP. In 11 women with titers 16-256 the HLA-DQB1 allele *0201 was found in 18%, i e as in a reference population. In 13 women with titers > or = 512 the HLA-DQB1 allele *0201 was found in 85% indicating a correlation between severe Rh(D) immunization with high titers/quantification values and the DQB1 allele *0201. In this group the fetus was severely affected by the immunization and treatment during pregnancy was frequently needed. HLA phenotyping of women known to have anti-D antibodies early in pregnancy seems to be an effective way to assess the probability of severe hemolytic disease of the newborn.