Intravenous Rh immune globulin prevents alloimmunization in D- granulocyte recipients but obscures the detection of an allo-anti-K

Rh immune globulin (RhIG) has been used to prevent alloimmunization in D(-) recipients of apheresis platelet transfusions from D(+) donors that may contain up to 5 mL of D(+) red blood cells (RBCs). Granulocyte concentrates contain approximately 30 mL of RBCs and it has been necessary to give D(-) recipients granulocyte transfusions from D(+) donors. Intravenous RhIG has not yet been demonstrated to be effective in preventing D alloimmunization with granulocyte transfusions. Four D(-) recipients received multiple D(+) granulocyte transfusions from D(+) donors and multiple injections of intravenous RhIG at a standard dose of 600 microg for each D(+) transfusion. Two D(-) males with chronic granulomatous disease were given 32 and 13 daily granulocyte transfusions, 18 and 2 of which, respectively, were D(+). After the first dose of intravenous RhIG, both patients exhibited circulating anti-D that was undetectable 3 to 4 years later. Two patients with severe aplastic anemia were given 5 and 14 granulocyte transfusions, 4 and 7 of which, respectively, were D(+). Both patients died before the effectiveness of RhIG could be assessed. In one of these patients the indirect and direct antiglobulin tests became positive after the first dose of intravenous RhIG, which required that subsequent granulocyte transfusions from D(+) donors be crossmatched by immediate spin (IS) testing only. A delayed hemolytic reaction attributed to allo-anti-K occurred after granulocytes from a K(+) donor were given to this patient. These results suggest that intravenous RhIG can be used to prevent alloimmunization to D in D(-) patients receiving large quantities of RBCs from D(+) granulocyte transfusions. However, anti-D and other passive antibodies from RhIG prohibit the use of the antiglobulin crossmatch with antigen-positive granulocyte donor samples. It may be important to frequently collect new samples to screen for newly formed allo-antibodies when IS crossmatches are used in place of the antiglobulin crossmatch.     

Immunoprophylaxis using intravenous Rh immune globulin should be standard practice when selected D-negative patients are transfused with D-positive random donor platelets

A 67-year-old female developed excessive bleeding and thrombocytopenia following cardiovascular surgery. Her blood type was group A, D-. The only platelet products available in the transfusion service were random donor platelet concentrates from D+ donors. She was transfused with a pool of 6 D+ random donor platelet concentrates. Anti-D undetected in her pretransfusion serum by solid-phase antibody screen was present 11 days later. Retrospectively, the patient provided a history of having two pregnancies more than 40 years ago, prior to the availability of immunoprophylaxis by Rh immune globulin (RhIG). Although studies have shown that as many as 19 percent of D- people may develop anti-D following transfusion of platelets from D+ donors, there is no specific standard requiring immunoprophylaxis with RhIG to prevent Rh alloimmunization after transfusion of random donor platelet concentrates from D+ donors. In contrast, vigorous efforts are routine for preventing Rh alloimmunization in D- patients requiring red cell transfusions or D- females during pregnancy or after delivery of D+ newborns. The absence of a comparable practice standard for platelet transfusions is based, in part, on concern that intramuscular injections of conventional RhIG may cause local hemorrhage in thrombocytopenic persons. The recent availability of a Food and Drug Administration-approved preparation of intravenous RhIG makes Rh immunoprophylaxis in thrombocytopenic patients safe and practical. We recommend that intravenous RhIG be considered if it is necessary to transfuse random donor platelet concentrates from D+ donors to D- recipients. As a minimal standard, intravenous RhIG should be administered to all D- females of childbearing age who are recipients of pools of random donor platelet concentrates from D+ donors.     

Detection of anti-D following antepartum injections of Rh immune globulin

Antepartum prophylaxis using Rh immune globulin (RhIG) at 28 weeks of gestation is routine in unsensitized Rh-negative women. As various sources state that anti-D may be detected up to 6 months after administration, we reviewed the medical and laboratory records of all Rh-negative women who delivered at our institution during 1995. For 385 evaluable women, only 137 (35.6%) had anti-D demonstrable in their sera at delivery; 97.8 percent of these delivered within 75 days after administration of RhIG. Of 248 women (64.4%) who delivered in < 76 days after administration of RhIG, 134 (54%) had demonstrable anti-D. For 123 women who delivered between 76 to 95 days after RhIG, only 3 (2.4%) had demonstrable anti-D. Of 14 women who delivered more than 96 days after RhIG, none had anti- D at delivery. These data show that the 300-microg dose used in the United States may not be adequate for antepartum protection and that the detection of anti-D more than 100 days after the administration of RhIG should be viewed with suspicion.     

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

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 R(0)(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 R(0)(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 R(0)(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.     

A gel technology system to determine postpartum RhIG dosage

Failures of Rh immune globulin (RhIG) prophylaxis occur when the dose is too small. We report a test using a gel technology (GT) method to replace the Kleihauer-Betke (K-B) test to assess fetomaternal hemorrhage (FMH) and assist in determining the minimum necessary dose of RhIG. Cord blood (O, D+) was mixed with adult blood (O D-) to mimic an FMH of 10 mL, 20 mL, 28 mL, and 40 mL. Test samples were incubated with anti-D at known concentrations and centrifuged. The supernatant was titrated against D+ and D- red cells using GT and an interpretation of the required RhIG dose was made. Results were compared with the K-B test. Results were easily discernible and interpretations leading to determination of recommended RhIG dosage were reproducible. Correlation to standard K-B testing was confirmed. Elapsed time for result availability by GT testing was 60 minutes, with a direct technical time requirement of 30 minutes. The GT system is easier, objective, and quantitative, and compares well to the standard K-B test. A single procedure will allow assessment of the extent of FMH in the great majority of cases. This technique works well in determining the appropriate dose of anti-D required to treat D- patients with D+ newborns. There are potential cost savings in decreased use of RhIG, less direct technical time required, and more rapid availability of results.     

Mechanism of anti-D-mediated immune suppression--a paradox awaiting resolution?

During pregnancy, women can be immunized by fetal red blood cells (RBCs) of an incompatible blood group. Subsequent transplacental passage of the antibodies can result in fetal morbidity or mortality due to RBC destruction. The administration of anti-D antibodies to D(-) women after delivery of a D(+) infant, and subsequent prevention of Rhesus (Rh) D haemolytic disease of the fetus and newborn, is the most successful clinical use of antibody-mediated immune suppression. The passive IgG anti-D might prevent immunization to D(+) RBCs by an IgG Fcgamma receptor (Fcgamma R)-dependent mechanism such as crosslinking the D-specific B-cell receptor and inhibitory FcgammaRIIb. However, recent murine studies demonstrate that the suppressive effects of antibodies to heterologous RBCs can be Fcgamma R-independent, suggesting other mechanisms might contribute.     

Update on HDFN: new information on long-standing controversies

Hemolytic disease of the fetus and newborn (HDFN) results from maternal IgG antibodies that cross the placenta to the fetal circulation during gestation and cause RBC destruction and complications before birth (HDF), or anemia and hyperbilirubinemia after birth (HDN), or both. In its most severe form,HDF produces hydrops fetalis, which is characterized by total body edema, hepatosplenomegaly, and heart failure and can lead to intrauterine death. Before discovery of Rh immunoglobulin (RhIG), HDFN from anti-D was a significant cause of perinatal mortality or long-term disability. Routine administration of RhIG to D- women during pregnancy and shortly after the birth of D+ infants effectively reduced the incidence of HDFN caused by anti-D. Maternal alloimmunization to other RBC antigens in the Rh, Kell, and other blood group systems can not be routinely prevented and these antibodies can also cause HDFN. Advances in prenatal care, noninvasive monitoring, and intrauterine transfusion have improved the outlook for affected pregnancies to the extent that even hydrops fetalis can be reversed and effectively treated in many cases. This review will provide an update on the current issues in prevention and treatment of HDFN, emphasizing recent insights into long-standing controversies regarding maternal weak D phenotypes and D alloimmunization, noninvasive fetal diagnosis and monitoring of affected pregnancies, and recent treatment guidelines.     

On the mechanism of tolerance to the Rh D antigen mediated by passive anti-D (Rh D prophylaxis)

Anti-D prophylaxis is the most successful clinical application of antibody-mediated immune suppression. Passive IgG anti-D is given to Rh D-negative women to prevent immunisation to foetal Rh D-positive red blood cells (RBC) and subsequent haemolytic disease of the newborn. Despite its widespread use and efficacy, the mechanism of action of this therapy is unproven. The known facts about the antigen, antibody response, dose of anti-D, RBC clearance and effects of the passive anti-D on subsequent primary and secondary immune responses are discussed in relation to recent information on ways by which immune responses may be suppressed. Most Rh D antigen sites on RBC are not bound by passive anti-D, and thus epitope masking (which may occur in experimental murine models using xenogeneic RBC) is not the reason why anti-D responses are prevented by administration of prophylactic anti-D. It is hypothesised that although clearance and destruction of the antigenic RBC may be a contributing factor in preventing immunisation, down-regulation of antigen-specific B cells through co-ligation of B cell receptors and inhibitory IgG Fc receptors must also occur.     

Rh(D)阴性孕妇产前免疫抗体水平与新生儿溶血病的关系

目的探讨Rh(D)阴性孕妇产前免疫抗体状态与新生儿溶血病的关系。方法回顾分析2003~2006年,35例RH(D)阴性孕妇的妊娠、分娩及其IgG抗D效价情况。结果在35例Rh(D)阴性孕妇中,初次妊娠18例,均未产生抗-D;两次以上妊娠17例,有5例产生抗-D,其中2孕次2例,效价均为1:2;3孕次2例,效价为1:8和1:32;4孕次1例,效价为1:256。结论在初次妊娠的Rh(D)阴性孕妇中,未见抗-D产生,孕次愈多,检测到的抗-D机率愈高;Rh抗体产生与个体免疫有关。     

In vivo studies of monoclonal anti-D and the mechanism of immune suppression.

Administration of anti-D immunoglobulin to D- women after delivery of a D+ infant has dramatically reduced the number of immunised women and cases of haemolytic disease of the fetus and newborn. The use of monoclonal anti-D might alleviate some of the pressures on maintaining adequate supplies of plasma sourced anti-D. Two human monoclonal antibodies, BRAD-3 (IgG1) and BRAD-5 (IgG3), with proven activity in in vitro functional (immunological) assays with cells bearing IgG Fc receptors (Fc gamma R) were selected for clinical studies. They were prepared by purification of IgG secreted by culture of the Epstein-Barr virus-transformed B cell lines in hollow fibre bioreactors. The clearance of D+ red cells injected into D- subjects was accelerated by prior injection of the monoclonal antibodies, both individually and blended (3:1, BRAD-5: BRAD-3). The subjects were protected from Rh D immunisation. A large multicentre study evaluated the BRAD-3/5 blend for its ability to prevent Rh D immunisation in 95 D- subjects given 400 micrograms i.m. 24 hours after injection of 5 ml D+ red cells. Challenge injections of D+ red cells alone were given 24 and 36 weeks later, and blood samples were taken every 4 weeks from the subjects throughout the study for detection of anti-D responses. There was one definite and one possible failure of protection; in one subject the plasma anti-D level rose from week 12 onwards, and in another individual rapid seroconversion was observed at week 28. Considering the relatively large dose of red cells and the number of subjects studied, it was concluded that the failure rate was much lower than in routine Rh D prophylaxis. The responder rate was 13% by week 36 and 24% by week 48. The low percentage of responders and the modest levels of endogenous anti-D produced suggested that administration of monoclonal anti-D had induced long-term specific suppression of anti-D responses in these subjects. The most likely mechanism of action was considered to be inhibition of B cells resulting from co-crosslinking antigen receptors with inhibitory Fc gamma R when the B cells contacted red cells that had bound passive anti-D.     

Detection of an antigen on the inner surface of Rh negative erythrocytes which binds anti-D IgG

Previous investigation have demonstrated the presence of the Rho(D) antigen in Rh negative erythrocytes. The intact Rh negative cell, however, does not bind anti-D IgG. Presently we have shown that an anti-D binding antigen resides on the cytoplasmic surface of Rh negative erythrocyte membranes. Unsealed Rh negative membranes, in which both the inner and outer surface are exposed, bind anti-D IgG. Dicyclohexylcarbodiimide specifically blocked the binding of anti-D IgG to these membranes. Sealed Rh negative membranes which expose only their external surface, failed to bind anti-D antiserum. These results were confirmed by proteolytic digestion of membrane preparations and subsequent Rho(D) antigen purification. Only when protease had access to the inner surface of Rh negative erythrocyte membranes did degradation of this 'D' antigen occur. Thus, intact Rh negative erythrocytes contain an antigen which binds anti-D antibody but is located on the inner surface of the membrane. In contrast, Rh positive erythrocytes expose Rho(D) antigen on the external surface of the membrane.     

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.     

Fcγ receptor expression on splenic macrophages in adult immune thrombocytopenia

Splenic macrophages play a key role in immune thrombocytopenia (ITP) pathogenesis by clearing opsonized platelets. Fcγ receptors (FcγR) participate in this phenomenon, but their expression on splenic macrophages and their modulation by treatment have scarcely been studied in human ITP. We aimed to compare the phenotype and function of splenic macrophages between six controls and 24 ITP patients and between ITP patients according to the treatments they received prior to splenectomy. CD86, human leucocyte antigen D‐related (HLA‐DR) and FcγR expression were measured by flow cytometry on splenic macrophages. The major FcγR polymorphisms were determined and splenic macrophage function was assessed by a phagocytosis assay. The expression of the activation markers CD86 and HLA‐DR was higher on splenic macrophages during ITP compared to controls. While the expression of FcγR was not different between ITP and controls, the phagocytic function of splenic macrophages was reduced in ITP patients treated with intravenous immunoglobulin (IVIg) within the 2 weeks prior to splenectomy. The FCGR3A (158V/F) polymorphism, known to increase the affinity of FcγRIII to IgG, was over‐represented in ITP patients. Thus, these are the first results arguing for the fact that the therapeutic use of IVIg during human chronic ITP does not modulate FcγR expression on splenic macrophages but decreases their phagocytic capabilities.     

Transfusions of rhesus-incompatible platelet concentrates in Rouen University Hospital: procedures and consequences]

INTRODUCTION: Guidelines for distribution and use of blood products have been established for both blood transfusion institution and hospitals, in particular for the use of Rh (D)-incompatible platelet concentrates. The aim of this study was to evaluate: 1) the rate of attribution for the Rh (D)-incompatible platelets concentrates, 2) the immunisation prophylaxis practices, 3) the immunological consequences using short and medium term follow-up of transfused patients. METHODS: Patients with Rh (D)-incompatible platelets concentrate administered during the year 2003 at Rouen University Hospital were retrospectively selected. Patients on transfusion were described. The relationship of various factors with the injection as well as the appearance of allo-immunization was statistically tested. RESULTS: During a year, 280 Rh (D)-incompatible platelets concentrates were administered to 67 patients. Immunisation prophylaxis by injection of Ig anti-D was not systematically performed. Four immunizations in the Rhesus group system were identified: 2 against D antigen (Ag), 1 against E Ag and 1 against C Ag. Immunisations against D Ag occurred for two younger women considered as immunodeficient. Immunization prophylaxis was more frequent in poly-transfused patients. However no difference was observed for the other factors. CONCLUSION: Compatibility concerning Rhesus (D) is not always possible. The immunization against red cells persists, in particular against the antigens of the Rhesus group system and moreover for the immunodeficient patients. Recommendations for immunization prophylaxis by injection of specific anti-D immune-globulin (Ig) could be reconsidered.     

Policies and procedures related to weak D phenotype testing and Rh immune globulin administration. Results from supplementary questions to the Comprehensive Transfusion Medicine Survey of the College of American Pathologists

OBJECTIVE: To determine and evaluate policies and procedures related to weak D phenotype testing and terminology and the administration of Rh immune globulin in selected clinical situations. Design, Setting, and Participants.-Institutions participating in the College of American Pathologists 1999 J-A Comprehensive Transfusion Medicine Survey program were asked to respond to a series of supplementary questions related to weak D phenotype testing and Rh immune globulin administration. More than 3500 institutions and transfusion services participated. RESULTS: Most supplementary questions elicited more than 3000 responses. Despite no clinical or regulatory mandate, 58. 2% of transfusion services routinely perform an antiglobulin test for the weak D phenotype in patients who test negative with anti-D reagents. Significant differences were found concerning the transfusion of blood components to patients with the weak D phenotype and the administration of Rh immune globulin to these individuals. At least one patient with the weak D phenotype with anti-D alloantibody formation was observed during a 12-month period by 31.8% of transfusion services. CONCLUSIONS: Significant variability concerning policies and procedures related to weak D typing and terminology was found in this survey. Transfusion of blood components to patients with the weak D phenotype and the administration of Rh immune globulin also demonstrated variations. Anti-D alloantibody formation by patients with the weak D phenotype may not be as rare as previously thought. Additional study related to the clinical significance of these results is warranted.     

Effect of danazol in immune thrombocytopenic purpura

Danazol and vinblastine are effective in many patients with chronic immune thrombocytopenic purpura (ITP). To evaluate the mechanism of action of these drugs, we studied six consecutive patients with chronic ITP treated with danazol and one treated with vinblastine. All the patients responded clinically without a notable change in the level of platelet-associated IgG. Instead, the clinical response to therapy was associated with a decrease in the number of monocyte binding sites for monomeric IgG (Fc receptors). In one patient, clinical relapse was associated with a spontaneous 2.7-fold increase in the number of monocyte Fc (IgG) receptors, without a change in the level of platelet-associated immunoglobulin. A decrease in the number of monocyte Fc (IgG) receptors following vinblastine infusion was associated with a clinical remission. We conclude that the clinical course of ITP may be influenced by the expression of monocyte or macrophage Fc (IgG) receptors. Danazol and vinblastine may mediate their clinical effect, at least in part, by influencing the number of available Fc (IgG) receptors on phagocytic cells.     

Effect of Membrane Cholesterol Depletion on the Immunoreactivity of the D Antigen and IgG Anti-D

The Immunoreactivity of the main Rh antigen (D) and Its corresponding antibody, as determined by a IgG to IgG combining ratio, antibody dissociation and antigen accessibility to antibody, was examined In cholesterol depleted human red cells and ghost membranes. The anti-IgG reactivity of IgG anti-D bound to cholesterol depleted red cells and ghosts was demonstrably enhanced in vitro and in electron microscopy studies, particularly in ghosts. Dissociation of cell bound anti-D during buffer incubation was greater after cholesterol depletion, especially in ghosts. There was also reduced binding of anti-D to cholesterol-depleted eel is as previously reported. All these effects appeared to be independent of endogenous or exogenous proteolysis in either cholesterol-depleted membranes or controls as Judged from membrane electrophoretic analyses. A₂C, an agent which increases membrane fluidity, had no effect on anti-D binding or the antiglobulin reactivity of cell bound IgG. A reduction in anti-D binding also was observed In red cells depleted of cholesterol following Immobilization of membrane proteins by glutaraldehyde crosslinking. The findings show that cholesterol depletion not only affects the antigen but also Rh antibody reactivity. They also suggest that factors other than vertical antigen movement in a fluid bi layer may influence the behavior of the D antigen in cholesterol-modified erythrocytes.     

Assessment of fetal-maternal haemorrhage in mothers with hereditary persistence of fetal haemoglobin.

Kleihauer examination of peripheral blood cannot be used reliably to detect transplacental fetal-maternal haemorrhage in mothers with hereditary persistence of fetal haemoglobin (HPFH). In Rh(D) negative pregnancies diagnostic confusion with a large fetal-maternal haemorrhage could result in the administration of inappropriately excessive amounts of anti-D immunoglobulin, and the inability to diagnose and quantify transplacental haemorrhage in maternal HPFH by current methods could result in insufficient anti-D administration and subsequent Rh(D) sensitisation. Accordingly, a method to detect and quantify fetal-Rh(D) positive maternal haemorrhage using erythrocyte fluorescent immunocytometry was developed. An indirect immunofluorescence method with IgG anti-D immunoglobulin as the primary antibody was used, combined with quantitative analysis on a fluorescence activated cell sorter. The method was accurate, specific, and sensitive and could detect a contaminating population of 0.1% Rh(D) positive cells in Rh(D) negative blood--a level of fetal-maternal haemorrhage well covered by a single dose of 500 IU of anti-D immunoglobulin.     

Plasma half-lives and bioavailability of human monoclonal Rh D antibodies BRAD-3 and BRAD-5 following intramuscular injection into Rh D-negative volunteers.

Two human MoAbs, BRAD-3 (an IgG3 anti-D) and BRAD-5 (an IgG1 anti-D), were produced from Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines grown in hollow fibre bioreactors. Six Rh D-negative male volunteers were injected intramuscularly with anti-D; two received BRAD-3 (approx. 1500 micrograms, 2600 IU), two were given BRAD-5 (300 micrograms, 2000 IU), and two had polyclonal anti-D immunoglobulin (500 IU, approx. 100 micrograms anti-D). Levels of anti-D in plasma samples taken up to 42 days later were measured by a sensitive AutoAnalyser method. The half life of BRAD-5 (mean 22.2 days) was greater, and that of BRAD-3 (mean 10.2 days) less than that of polyclonal anti-D (mean 15.6 days). The bioavailability (plasma uptake) of the MoAbs (mean 33.9%) was less than that of the polyclonal anti-D (mean 60.3%). BRAD-3 and BRAD-5 may be suitable for use in antenatal and post-natal prophylaxis against Rh D haemolytic disease of the newborn.     

The occurrence of circulating immune complexes and viral antigens in idiopathic thrombocytopenic purpura.

The sera of seventy-two patients with ITP were tested for their inhibitory activity on the agglutination of IgG-coated particles by RF or C1q. The majority (83%) displayed an inhibitory effect toward both agglutinators, whereas 17% were found to contain endogenous RF. A negative correlation was observed between the number of platelets and the titres of inhibitory factors. Some sera were fractionated by gel filtration. The inhibitory factors and sometimes trace amounts of IgG were distributed over several peaks eluted before monomeric 7S IgG. The IgG detected in the heavy fractions of two ITP sera corresponded to antigen-antibody complexes as shown by dissociation experiments at acid pH. In all ITP sera analysed by chromatography, DNA has been detected in the heavy fractions and appears to be the antigen of certain complexes. The sera from forty-two patients with ITP were analysed by counter-electrophoresis for the presence of viral antigens. HBs antigen was detected in twenty sera, EBV antigen in five, and adenovirus antigen in six.