Stability of murine monoclonal anti-A, anti-B and anti-A,B ABO grouping reagents and a multi-centre evaluation of their performance in routine use

Predictive modeling of complex ABO glycan phenotypes by lectin microarrays

Serological classification of individuals as A, B, O, or AB is a mainstay of blood banking. ABO blood groups or ABH antigens, in addition to other surface glycans, act as unique red blood cell (RBC) signatures and direct immune responses. ABO subgroups present as weakened, mixed field, or unexpected reactivity with serological reagents, but specific designations remain complex. Lectins detect glycan motifs with some recognizing ABH antigens. We evaluated a 45-probe lectin microarray to rapidly analyze ABO blood groups and associated unique glycan signatures within complex biological samples on RBC surface glycoproteins. RBC membrane glycoproteins were prepared from donor RBCs, n = 20 for each blood group. ABO blood group was distinguishable by lectin array, including variations in ABH antigen expression not observed with serology. Principal component analysis highlighted broad ABO blood group clusters with unexpected high and low antigen expression and variations were confirmed with ABH antibody immunoblotting. Using a subset of lectins provided an accurate method to predict an ABO serological phenotype. Lectin microarray highlighted the importance of ABO localization on glycoproteins and glycolipids and pointed to increased glycocalyx complexity associated with the expression of A and B antigens including high mannose and branched polylactosamine. Thus, lectins identified subtle surface ABO blood group glycoprotein density variations not detected by routine serological methods. Transfusion services observe alterations in ABH expression during malignancy, and ABO incompatible solid organ transplantation is not without risk of rejection. The presented methods may identify subtle but clinically significant ABO blood group differences for transfusion and transplantation.

A 24-base pair deletion in the ABO gene causes a hereditary splice site defect: a novel mechanism underlying ABO blood group O

BACKGROUND

Blood group A and B antigens are synthesized by glycosyltransferases regulated by a complex molecular genetic background. A multibase deletion in the ABO gene was identified in two related blood donors. To define its hereditary character and to evaluate genotype-phenotype associations, a detailed study including 30 family members was conducted.

METHODS AND MATERIALS

ABO phenotyping was performed with agglutination techniques and adsorption-elution tests. The secretor status was determined. Allele-specific sequencing of ABO and genotyping of family members by a mutation-specific polymerase chain reaction were carried out. Functional analysis included cloning of complementary DNA and transfection experiments in HeLa cells. The antigen expression was investigated by flow cytometry and adsorption-elution method.

RESULTS

Sequencing analysis revealed a 24-bp deletion in Exon 5 and the adjacent intronic region of ABO. The alteration was inherited by 16 family members. Nine of them being heterozygous for the mutated allele failed to express A antigen on their erythrocytes as found by routine typing. In particular samples, however, adsorption-elution studies indicated inconclusive results. HeLa cells transfected with aberrant gene transcripts did not express blood group antigen A.

CONCLUSION

The variation causes defects in messenger RNA splicing, most likely inactivating the transferase as observed by serological typing and in vitro expression analysis. These data suggest a novel mechanism associated with blood group O and extend the knowledge of exceptionally rare ABO splice site mutations and deletions. With increased understanding of the molecular bases of ABO, the diagnostics may be further enhanced to ensure the safest possible use of the blood supply.

The preparation, characterization, and application of environment-friendly monoclonal antibodies for human blood cell

OBJECTIVES

Monoclonal anti-human blood group A (51A8) and B (63B6) antibody reagents were prepared using the serum-free technique. The aims of this research were to characterize the serum-free reagents and prove their reliabilities in routine use.

METHODS

Experiments including antigen-antibody agglutination testing, stability testing, SDS-PAGE, protein and IgM quantification, flow cytometry, and variable domain sequencing were performed to characterize the anti-A (51A8) and anti-B (63B6) reagents. Over 12 000 samples were tested using these reagents as routine blood grouping reagents.

RESULTS

Serum-free anti-A (51A8) and anti-B (63B6) reagents were stable in longitudinal and accelerated testing, and their high purity was shown in SDS-PAGE and IgM quantification. These reagents have high specificity to red blood cells in serologic agglutination testing and flow cytometric analysis. A1 and A2 subgroup antigens can be distinguished clearly by patterns of flow cytometric histograms. No discrepancy was found in clinical trials of 12 000 samples.

DISCUSSION

To reduce the risk of being affected by any animal additives, a serum-free culture system was applied to get mass-production of monoclonal anti-A/B antibodies. The high specificity and the high purity of the reagents were verified by the lab experiments.

CONCLUSION

Lab research and clinical trial showed that serum-free monoclonal anti-A (51A8) and anti-B (63B6) reagents meet the requirements of routine blood grouping reagents. Moreover, these reagents featured ultra-high purity that is missing in other commercial counterparts, and therefore are recommended as more environment-friendly reagents.

Mapping the fine specificity of ABO monoclonal reagents with A and B type-specific function-spacer-lipid constructs in kodecytes and inkjet printed on paper

BACKGROUND

Monoclonal (MoAb) reagents are routinely used and are usually very reliable for the serologic determination of ABO blood types. However, the fine specificity and cross-reactivity of these reagents are often unknown, particularly against synthetic antigens used in some diagnostic assays. If nonserologic assays or very sensitive techniques other than those specifically prescribed by the manufacturer are used, then there is a risk of incorrect interpretation of results.

STUDY DESIGN AND METHODS

Forty-seven MoAbs and two polyclonal ABO reagents were tested against red blood cell (RBC) kodecytes prepared with A trisaccharide, A Type 1, A Type 2, A Type 3, A Type 4, B trisaccharide, B Type 1, B Type 2, acquired B trisaccharide, and Le(a) trisaccharide function-spacer-lipid (FSL) constructs. Natural RBCs were tested in parallel. In addition these FSL constructs were printed onto paper with a desktop inkjet printer and used in a novel immunoassay that identifies reactivity through the appearance of alphanumeric characters.

RESULTS

Mapping of MoAbs with kodecytes and printed FSL constructs revealed a series of broad recognition patterns. All ABO MoAbs tested were reactive with the RBC dominant Type 2 ABO antigens. Unexpectedly some anti-A reagents were reactive against the B Type 1 antigen, while others were poorly reactive with trisaccharide antigens.

CONCLUSIONS

All ABO MoAbs detect the RBC dominant Type 2 ABO antigens; however, some reagents may show minor reactivity with inappropriate blood group antigens, which needs to be considered when using these reagents in alternative or highly sensitive analytic systems.

Immunochemical characterization of the Rh CW antigen using human monoclonal antibodies

BACKGROUND AND OBJECTIVES

Human monoclonal antibodies have been produced against various Rh antigens. We report here the production of another one against Rh C and the first such antibody against Rh CW.

MATERIALS AND METHODS

Two heterohybridomas secreting IgG human monoclonal antibodies against Rh CW and Rh C (MS-353 and MS-242 respectively) were produced from alloimmunized donors. Their specificity was confirmed by serological testing.

RESULTS

MS-353 reacted with all CW-positive phenotypes but not with any CW-negative phenotypes, whereas MS-242 reacted with all CW-positive and C-positive phenotypes. Using 125I-labelled antibodies, the average number of CW sites/red cell was 32,000 (R1WR1W, 15,200 (R1WR1), 19,800 (R1WR2), 15,300 (R1Wr), 26,200 (r'Wr), and the average number of C sites per red cell on equivalent CW/C-positive phenotypes was similar: 22,400 (R1R1), 21,800 (R1WR1), 12,300 (R1R2), 11,700 (R1WR2), 13,400 (R1r), 15,100 (R1Wr), 21,100 (r'r), 18,700 (r'Wr). MS-353 and MS-242 were mutually inhibitory. Both antibodies specifically immunoprecipitated a 33- to 34-kD polypeptide from 125I-surface-labelled cells.

CONCLUSION

MS-353 is suitable for the serological detection of CW-positive cells, and the immunochemical data are entirely consistent with the report that the CW antigen is associated with a point mutation in the RHCE gene [Blood, 1995;86:1196-1201].

Production of stable human-mouse hybridomas secreting monoclonal antibodies against Rh D and c antigens

Peripheral blood lymphocytes from donors immunized against Rh antigens were fused with mouse myelomas and heteromyelomas in order to obtain human-mouse hybridomas secreting antibodies specific for these antigens. Three cell lines secreting anti-D IgG and two secreting anti-c IgM were stabilized and produced immunoglobulins for several months. These human monoclonal antibodies were evaluated as reagents for Rh phenotyping. Their complementary activity towards weak D and partial D antigens is examined.

A new monoclonal anti-A antibody BIRMA-1. A potent culture supernatant which agglutinates Ax cells, but does not give undesirable reactions with B cells

A monoclonal anti-A antibody, BIRMA-1, has been evaluated and found to be eminently suitable as a blood-grouping reagent. The culture supernatant is potent, avid and specific as demonstrated by its reactivity with a large sample of donor bloods tested manually and on the Olympus PK 7100 automated blood grouping machine. Over 100 cord blood samples were tested manually, and all were correctly grouped using this antibody. No false-positive reactions were obtained with papainized group B cells. Reagent prepared from BIRMA-1 detected most examples of Ax and all other A subgroups and A variants tested. Negative reactions with B(A) cells indicate that it is possible to have an antibody capable of detecting Ax which will not react with B cells from individuals with high levels of galactosyltransferase.

Immunocytochemical determination of ABH and MN antigens on dried blood traces in the nanoliter range

The absorption-elution test and the mixed cell agglutination reaction are both ultimately based on the ability of indicator cells to agglutinate. This agglutination reaction requires a relatively large amount of antigenic epitopes, and, in addition, a relatively high volume of blood traces. The immunocytochemical demonstration of epitopes requires a lower volume, which, however must be fixed for investigation, thus possibly causing damage to the epitopes and thereby preventing detection. An immunocytochemical method is presented which permits ABH and MN antigen determination on dried blood traces of nanoliter quantities without special fixation. This method is based on immunocytochemical demonstration of antigens directly on the cell membrane in combination with the use of a coated glass slide that ensures maximum economy of epitopes.

Developing techniques in blood transfusion

Expansion of transfusion medicine has led to an increasing awareness of the importance of its practice. Specialists in this branch of haematology whose main aim is to provide adequate and safe supplies of blood (and blood products) and to ensure these are used appropriately, are increasingly aware that to do this efficiently requires the development and utilization of new laboratory and technical procedures. Review of cross-matching techniques has led to the introduction of more rapid methods using low ionic strength saline. Use of monoclonal antibodies for blood grouping has made use of new technology, whilst allowing scarce human plasma to be used more appropriately for therapeutic purposes. Similarly, the implementation of a more rational approach to blood ordering, as in a maximum surgical blood-order schedule, allows for the more efficient use of donor blood. The use of microtitre plates for grouping and cross-matching techniques allows for speed and economy in the transfusion laboratory. Their use is also associated with increased automation and computer use. The possibility of using solid-phase techniques, monocyte-macrophage assays and antibody-dependent cellular cytotoxicity assays introduces new techniques differing markedly from time-honoured liquid-phase serology methods. The application of flow cytometry, which has already been shown to be useful in many aspects of haematology, is also of benefit in the field of blood transfusion science. Safety of blood transfusion is an important aspect of its practice and has led to the introduction and development of screening tests for donor blood to exclude infection risks from such organisms as HIV-1, hepatitis B and non-A, non-B hepatitis. Another approach to ensure the safety of transfused blood has been increased usage of autologous transfusion by means of both predeposit donation and intraoperative cell salvage.