Flow cytometric analyses of the subclasses of red cell IgG antibodies

Efficacy of D- red blood cell transfusion and rituximab therapy in autoimmune hemolytic anemia with anti-D and panreactive autoantibodies arising after hematopoietic stem cell transplant

BACKGROUND

Autoimmune hemolytic anemia (AIHA) is caused by autoantibodies to red blood cells (RBCs), which can be panreactive and/or specific to Rh/other blood group antigens. We report a severe case of AIHA after bone marrow transplantation (BMT) due to autoanti-D triggered by reactivation of Epstein-Barr virus (EBV) infection. A combined strategy of D- RBC transfusion and administration of anti-CD20 monoclonal antibody (MoAb) resolved the hemolysis.

CASE REPORT

A 33-year-old male underwent allogeneic BMT from an ABO-identical and HLA-matched unrelated male donor. Five months later, while having mild chronic graft-versus-host disease, he manifested AIHA, with a hemoglobin (Hb) level of 5.1 g/dL on AIHA Day 2 (Posttransplant Day 156) and was refractory to D+ RBCs, with a Hb level of 2.4 g/dL on AIHA Day 6. Anti-D-like autoantibodies (titer 1280, subclass immunoglobulin G₁ , monocyte monolayer assay 28.7%) and panreactive (titer 40) were identified. Changing the RBC transfusion strategy to D- increased his Hb level to 6.7 g/dL on Day 10. Administration of anti-CD20 MoAb mitigated EBV-related B-cell proliferation and reduced anti-D autoantibody titer to 320 by Day 16 with normalized Hb concentration after 6 months.

CONCLUSION

In severe AIHA, when standard treatment and regular RBC transfusions are ineffective, transfusion of RBCs lacking the target antigen(s) of autoantibodies and administration of anti-CD20 MoAb should be considered.

Haemoglobin levels in autoimmune haemolytic anaemias at diagnosis: relationship with immunoproteins on red blood cells

Previous investigations of the relationship between characteristics of immunoproteins on red blood cells (RBCs) and the occurrence of autoimmune haemolysis yielded divergent results. Here, we studied these characteristics in autoimmune haemolytic anaemias (AIHAs) to determine their relationship with the degree of anaemia at diagnosis. We studied at diagnosis 52 cases of warm AIHA with positive direct antiglobulin test. Immunohaematological testing and determination of immunoglobulin class, complement, and immunoglobulin G (IgG) were performed using gel technology (GCT). Median haemoglobin (Hb) levels significantly differed between cases with IgG1 only or negative for IgG subclasses (7.4 g/dl), those with IgG3 or IgG1 + IgG3 (6.5 g/dl), and those with multiple immunoglobulins (5 g/dl). Logistic regression indicated that IgG3 detection was the only variable significantly related to the occurrence of RBC transfusion in AIHA (odds ratio 4.05, 95 % CI 1.1-14.7). In our study, the type of immunoprotein(s) on the RBC surface was associated with different Hb levels at AIHA diagnosis. IgG3 and multiple immunoglobulins were associated with lower Hb levels; IgG3 was also associated with a higher percentage of patient transfusions in the first week after diagnosis. Thus, qualitative differences in these immunoproteins may lead to deeper and more prolonged anaemia levels, influencing the need for RBC transfusion.

Autoimmune hemolytic anemia with gel-based immunohematology tests

We used gel centrifugation tests (GCTs) to analyze the relationship between the diagnosis and immunohematology tests used for autoimmune hemolytic anemia (AIHA). The study included 588 samples positive for the direct antiglobulin test (DAT). Of these, 52 were from patients diagnosed with AIHA. Immunoglobulin (Ig) class, IgG1, IgG3, and complement were measured. DAT strength had the strongest correlation with AIHA diagnosis (odds ratio [OR], 23), followed by anti-IgG titer 300 (OR, 8.4), anti-IgG titer 1,000 (OR, 10.5), and C3d agglutination strength (OR, 1.7). Decision tree analysis revealed that DAT strength and anti-IgG titer higher than 100 were the best predictors of AIHA. Multidimensional scanning analysis found a high grade of similarity among DAT strength, anti-IgG titer, and IgG strength in the AIHA samples. This observation was not detected in DAT-positive samples from patients without AIHA. DAT strength remained the best diagnostic indicator for AIHA and had the strongest association with AIHA compared with other commercially available immunohematology tests. The other tests, despite good correlation with AIHA diagnosis, did not add useful information.

Diagnostic laboratory technologies for the fetus and neonate with isoimmunization

Maternal-fetal blood group incompatibility is common but less commonly results in hemolytic disease of the fetus and newborn (HDFN). HDFN is associated with greater peak bilirubin, at an earlier age, and for longer duration than other causes of hyperbilirubinemia. It poses a substantial risk for kernicterus and accounts for the majority of exchange transfusions for hyperbilirubinemia. Advances in diagnosis and management are described, from identification of the alloimmunized pregnancy by maternal ABO and Rh typing, antibody screen (indirect Coombs test), identification and titration; laboratory evaluation of the maternal-fetal unit with a critical maternal antibody titer to prompt fetal antigen status determination; assessment of fetomaternal hemorrhage by conventional Kleihauer-Betke testing or by flow cytometric methodology; to antenatal management of isoimmunization and fetal status assessments using the systems of Liley, Queenan, and serial Doppler fetal middle cerebral artery peak velocity measurements. The utility of laboratory diagnostics in the approach to hemolysis in the neonate, including hematology, chemistry, and peripheral blood smear review, is reviewed. The goal of management, to deliver a healthy infant at or near term, is attained for the majority of cases using current modalities; future directions include noninvasive genotyping of fetal blood from maternal serum to fully eliminate RhD alloimmunization and HDFN; and development of prophylaxis and intervention strategies for non-RhD alloimmunizations for which immune globulin is currently unavailable.

Isotype-specific detection of ABO blood group antibodies using a novel flow cytometric method

Several methods to detect anti-A/B antibodies based on haemagglutination and haemolysis have been described. These methods measure predominantly anti-A/B immunoglobulin (Ig)M, whereas anti-A/B IgG and IgG subclasses are less well examined. We established a flow cytometry method (ABO-fluorescence-activated cell sorting; ABO-FACS) to quantify binding of anti-A/B IgM, IgG and IgG subclasses to human A or B red blood cells. Anti-A/B IgM were present in the majority of 120 blood donors, as expected from blood group typing. The sensitivity and specificity of anti-A/B IgM to predict the blood group was 93% and 96% respectively. Anti-A/B IgG was found in 34/38 blood group O samples (89%). Anti-B IgG in blood group A or anti-A IgG in blood group B was present in 4/28 (14%) and 1/28 (4%) samples, respectively, and absent in 26 AB sera. IgG2 was the predominant IgG subclass. The correlation of anti-A/B IgM and IgG in the ABO-FACS with haemagglutination titres was 0.870 and 0.783, respectively (n = 240; P < 0.001) whereas the comparison of ABO-FACS with ABO-enzyme-linked immunosorbent assay was less significant. In conclusion, ABO-FACS is a valid method to quantify anti-A/B IgM, IgG and IgG subclasses. It opens the possibility of isotype-specific monitoring of anti-A/B antibodies levels after ABO-incompatible solid organ and stem cell transplantation.

A newly developed gel centrifugation test for quantification of RBC-bound IgG antibodies and their subclasses IgG1 and IgG3: comparison with flow cytometry

BACKGROUND

Novel gel centrifugation test (GCT) cards were evaluated with respect to their ability to estimate the quantity of IgG on RBCs and the determination of the IgG subclasses IgG1 and IgG3.

STUDY DESIGN AND METHODS

In 65 patients with a positive DAT, the amount of IgG-gamma-, IgG1, and IgG3 on RBCs was examined by use of GCT cards and flow cytometry (FC) in parallel. The results were correlated with the presence or absence of hemolysis. In addition, D+ RBCs were studied after sensitization with anti-D sera from 22 alloimmunized pregnant women.

RESULTS

The amount of IgG on the RBCs as determined by GCT dilution cards correlated with FC (r=0.70, p < 0.0001). IgG subclass results as determined by GCT IgG subclass cards were confirmed by FC in 14 cases with an anti-IgG-gamma-chain titer > or =300, whereas IgG subclass cards were not suitable in cases with anti-IgG-gamma-chain titers less than 300. In 44 patients with 2+ or 3+ DAT in the GCT and anti-IgG-gamma-chain titer < or =30, no hemolysis was observed, whereas hemolysis occurred in 13 of 14 patients with an anti-IgG-gamma-chain titer > or =300. GCT data obtained by IATs with anti-D sera were concordant with FC results.

CONCLUSION

There is a correlation between the amount of RBC-bound IgG and immune hemolysis. The GCT cards that detect the anti-IgG-gamma-chain may be useful to predict hemolysis in patients with a 2+ or 3+ DAT in the GCT. The diagnostic value of GCT cards for IgG subclass testing should be investigated further.

Severe HDN due to anti-Ce that required exchange tranfusion

BACKGROUND

Rh system antibodies are commonly encountered in blood bank practice as well as during pregnancy. Nevertheless, no examples of anti-Ce (RH7) have been reported as a cause of HDN that requires exchange transfusion.

CASE REPORT

A 38-year-old woman in her fourth pregnancy was typed as blood group O D+, C-, c+, E+, e-. Anti-C and anti-e were detected in her serum during a routine prenatal work-up. Further evaluation, including flow cytometric analysis, revealed the presence of a strong anti-Ce and a weak anti-e. Her partner was typed as group A D+, C+, c-, E-, e+. A seemingly healthy male infant was delivered at 40 weeks of gestation. The infant's RBCs were typed as group O D-, C+, c+, E+, e+ with a positive DAT (titer 128). Twenty-five hours after birth, the baby had to be transferred to the neonatal intensive care unit because of rapidly rising total serum bilirubin. Despite intensive treatment, including double phototherapy, albumin infusion, and the administration of furosemide and IVIG, the total serum bilirubin level increased during the following day and exchange transfusion with 2 units of type O D-, C-, c+, E+, e- had to be performed; this resulted in a prompt decrease in total serum bilirubin without relapse.

CONCLUSION

Anti-Ce caused severe HDN requiring exchange transfusion. This highlights the need for a close follow-up throughout pregnancy if unexpected RBC antibodies are present, to permit the provision of compatible blood in case of a rare antibody.

Gel test assay for IgG subclass detection by GM typing: application to hemolytic disease of the newborn

The gel test assay was evaluated for IgG subclass detection by GM typing of antibodies and compared to the classical inhibition agglutination method on slides or microtiter plates. We used a panel of 5 murine monoclonal antibodies directed against G1M(1), G1M(3), G1M(17), G2M(23), and G3M(21) and 1 human polyclonal anti-G3M(5) antibody. Eleven polyclonal antisera (of immunized women) directed against red blood cells were tested for the GM allotypes carried by their alloantibodies. We controlled the specificity of the gel test reaction using a panel of anti-RH(D) monoclonal antibodies. All reagents exhibited a good reactivity and specificity. They can be used for routine typing. The gel test assay for IgG subclass detection is a specific, simple, and low-cost technique for the detection and management of severe forms of diseases in alloimmunized pregnancies.

Application of RHD and RHCE genotyping for correct blood group determination in chronically transfused patients

BACKGROUND

In chronically transfused patients, conventional blood group typing may be impossible because of mixed-field agglutination.

STUDY DESIGN AND METHODS

In 27 patients with congenital anemia and lifelong transfusion history, genotyping for D, RHD, and RHCE was performed with polymerase chain reactions. These results were compared with the blood group typing results documented in the medical record.

RESULTS

Two of 27 cases had been typed D-negative by serologic tests and D-positive by genotyping. In 20 patients, the CDE formula had been determined serologically according to the medical record; 4 of these patients were Cc by serologic tests and C/C by genotyping. One patient typed ee by serologic tests, and genotyping revealed heterozygosity (E/e).

CONCLUSION

In patients with a lifelong transfusion history, serologic blood group determination may be impossible, and pretransfusion test results are not always available or reliable. In whites, Rh-matched transfusions are possible with genotyping. The genetic background of the RH genes has to be elucidated in other ethnic groups, such as in black patients with sickle cell disease, before genotyping can be applied without restriction.

An overview of the use of flow cytometry in the analysis of mixed red cell populations

This paper reviews the application of flow cytometric techniques to the analysis and quantitation of mixed red cell populations. Such mixtures may arise in a variety of ways, for example: through transplacental hemorrhage during pregnancy or upon delivery; through iatrogenic procedures such as blood transfusion, bone marrow or peripheral blood stem cell transplantation; or through disease, when a loss of surface antigen expression may occur due to the expansion of abnormal progenitors lacking the appropriate gene or lacking the ability to translate the product of the gene. Flow cytometry can offer a simple and accurate means of identifying and quantitating mixed red cell populations through detection of antigens specific for either donor or recipient, and in many cases it is possible to distinguish homo- or heterozygous expression of a common antigen. Internal antigens may be accessed after fixation and permeabilisation of the red cells. These latter techniques are relatively new and expand the spectrum of antigenic differences available for the identification of individual species in mixed populations.

Immunoglobulin isotype identification in red cell antibodies using flow cytometry

BACKGROUND

Identifying the isotype of an immunoglobulin (IgM vs. IgG) detected in a patient sample is especially important in anticipating the risk of hemolytic disease of the newborn. Currently, 2-mercaptoethanol (2-ME) treatment of a sample is used in the authors' laboratory to degrade IgM, and this is followed by retesting. This method has multiple drawbacks. The purpose of this study was to develop a flow cytometry (FC) assay that would replace the 2-ME treatment protocol (2-ME treatment).

STUDY DESIGN AND METHODS

A preliminary FC assay was developed, modified, and refined through the use of stock antibodies. Then, 10 samples containing antibodies were tested in parallel by the FC assay and 2-ME treatment.

RESULTS

When a 10-unit mean channel fluorescence change was used as an index of a positive result, the FC assay detected all isotypes identified by 2-ME treatment. The FC assay was also able to identify mixtures of isotypes. One antibody that had not reacted in conventional agglutination testing was detected by the FC assay. The amount of fluorescence and the agglutinating strength of the antibody did not parallel each other. In one case, this discrepancy may have reflected an antibody that was primarily IgA.

CONCLUSIONS

The FC assay appears to be as accurate as 2-ME treatment in differentiating IgG from IgM. The FC assay produces a positive endpoint for both isotypes, will identify IgA, requires less sample, and has no odor.

Application of the gel test in IgG subclassing--a comparison of two agglutination assays

BACKGROUND AND OBJECTIVES

IgG subclasses of anti-D seem to play some role in hemolytic disease of the newborn, but there has been disagreement as to its exact nature. The aim of our study was to evaluate a new technique for IgG subclassing of anti-D and to compare it to an established test.

MATERIALS AND METHODS

In 31 cases of RhD immunization, we have compared two simple agglutinating assays for subclassing anti-D: an established V-well microtiter tray assay and a new gel test assay. Polyclonal rabbit anti-IgG agglutinating antibodies were tested against sensitized D-positive red blood cells by both assays.

RESULTS

The anti-D concentration in tested sera varied between 0.1 and 81 micrograms/ml (0.5-405 IU/ml). Both assays were simple to perform and the results correlated well.

CONCLUSIONS

The gel test had two advantages: quick performance and easy interpretation.