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D Voak

Publications and source records attributed to D Voak.

At least 19 recordsLinked to original sources
PubMed1992

The A1 (B) phenomenon: a monoclonal anti-B (BS-85) demonstrates low levels of B determinants on A1 red cells.

A monoclonal anti-B (BS 85) that reacts strongly with red cells from weak B variants (B3, Bint and Bv) has demonstrated the presence of a trace of B on A1 red cells. The agglutination of group A1 red cells by an anti-B antibody is called the A1 (B) phenomenon and is the converse of the B(A) phenomenon seen with certain monoclonal anti-A antibodies. Fragile A1 (B) agglutination is best seen by spin-tube techniques and A1 red cells negative in saline tests are agglutinated by albumin and protease enzyme-enhanced tests, but no reactions are seen with A2 red cells. The A1 (B) reaction is specifically inhibited by B substance, and D-galactose and the galactose-containing sugars melibiose and lactose. Red cells from B variants showed differential inhibition patterns with various sugars. A1 transferase levels were normal even in the strongest A1 (B) reactive blood samples, although the plasma H transferase levels and H status of these red cells were elevated. This is in contrast to the B(A) phenomenon which is associated with elevated levels of B transferase. It is suggested that A1(B) overlapping specificity can occur because of a combination of higher H activity (and thus more H sites) together with normal levels of A transferase activity as they are 20% higher than normal levels of B transferase. The production of anti-B reagents free of the A1 (B) phenomenon with BS-85 is achieved by suitable dilution using quality control tests with protease-treated A1 red cells.(ABSTRACT TRUNCATED AT 250 WORDS)

ABO Blood-Group System↗
PubMed1992

Bv: a distinct category of B sub-group among Chinese blood donors in Hong Kong.

During the period 1984-1989, a total of 46 examples of Bv phenotype were encountered out of a total of 567,210 donors, giving an incidence of 1 in 12,330 among the Chinese in Hong Kong. The Bv determinant corresponds to the portion of the B antigen that is present on rabbit red cells, and gives a negative reaction with polyclonal anti-B reagents absorbed with rabbit red cells that still react with B3. Some potent monoclonal anti-B reagents confirm the absence of a B epitope from Bv red cells even by adsorption and elution techniques. The failure of some monoclonal anti-B reagents to detect Bv demonstrates the need to select or blend monoclonal anti-B reagents for use in typing Oriental bloods. Cell-conversion techniques failed to convert O cells to B cells using Bv serum with the appropriate substrate, whereas sera from most of the other B variants were capable of doing so. The Bv phenotype, therefore, represents a distinct category of B subgroups that is easily distinguishable from B3 and other B variants.

ABO Blood-Group System↗
PubMed1990

Monoclonal antibodies as blood grouping reagents.

The large volume requirements for high quality ABO and Rh(D) typing reagents can now be supplied by selected monoclonal antibodies. Superior anti-A and anti-B monoclonal reagents can be prepared, from blends of at least two antibodies, to optimize the intensity of agglutination for slide tests and the potency for the detection of the weaker sub-groups, including Ax and Bw, by tube techniques. New quality control steps have been described for some highly sensitive anti-A/anti-B antibodies to avoid the detection of traces of A on B cells or traces of B on A1 cells, which results from the non-specific activity of A and B transferases. Excellent anti-A,B reagents may also be made by blends of at least two antibodies to optimize both A and B reactions, but the need for their continued use is now debatable. The development of high titre IgM monoclonal anti-D reagents offers simple rapid saline Rh(D) typing of both patients and donors, but they cannot reliably detect weak D (Du) and some D variants, e.g. the epitopes on D category VI cells. However, this can be achieved by blending an IgM anti-D with IgG (polyclonal) anti-D which can detect these types after conversion of negative saline tests to an antiglobulin phase. In addition, high grade Du, D categories and variants can be reliably detected (for typing donors) by selected monoclonal IgM and IgG anti-Ds by use of suitably enhanced tests without the use of an antiglobulin test.(ABSTRACT TRUNCATED AT 250 WORDS)

ABO Blood-Group System↗
PubMed1989

Further evidence for the presence of A antigen on group B erythrocytes through the use of specific exoglycosidases.

Certain antibodies have shown the ability to detect small amounts of A antigenic structures on certain group B cells. These rare cells that reverse group as B, are designated here as B(A) cells. Among the anti-A antibodies capable of detecting these cells are MHO4 (an IgM murine monoclonal antibody) and polyclonal anti-A derived from blood group O donors. The latter (anti-A, B) have been adsorbed exhaustively with normal B cells, to deplete the serum of antibodies to group B antigen. The cell specificity detected by these antibodies can be removed only by an alpha-N-acetylgalactosaminidase (A-zyme) but not by an alpha-galactosidase (B-zyme). Inhibition studies show that these reactions can be inhibited by A secretor saliva and cannot be inhibited by B secretor saliva. Moreover, papain treatment of normal group B cells not previously agglutinable with these antibodies, now causes these cells to become reactive, and this specificity, too, is removed only by A-zyme. These results suggest that low levels of blood group A antigen are being recognized by these antibodies and that these structures can exist not only on B(A) cells but on all group B erythrocytes.

ABO Blood-Group System↗
PubMed1989

Monoclonal blood group antibodies.

The large volume requirements for high quality AB0 and RhD typing reagents can now be supplied by selected monoclonal antibodies. Superior anti-A and anti-B monoclonal reagents are each prepared from blends of two antibodies to optimise the intensity of agglutination for slide tests and the potency for detection of the weaker sub-groups, including Ax and Bw by tube techniques. Excellent anti-A,B reagents must also be made by blends of at least two antibodies to optimise both A and B reactions, but the need for their continued use is now debatable. The development of high titre IgM monoclonal anti-D reagents offers simple rapid saline RhD typing of both patients and donors, but they cannot reliably detect weak D (Du) and some D variants (Cat. VI). However, this can be achieved by blending IgG (polyclonal) anti-D with the IgM anti-D which can detect these types (in donor bloods) after conversion of negative saline tests to an antiglobulin phase. Selected monoclonal anti-complement blended with conventional anti-IgG can provide excellent polyspecific anti-human globulin reagents free of 'false positives' in routine tests. Monoclonal anti-M and -N require careful pH adjustment for optimum reactions. All anti-N reagents must be carefully diluted for reliable detection of heterozyotes, but with freedom of cross reaction with S + MM cells that have the most 'N' that is not a product of the N gene. Specific anti-M monoclonal antibodies can occur and an example is described that does not agglutinate NN cells even as a neat supernatant.

ABO Blood-Group System↗
PubMed1988

Replicate tests for the detection and correction of errors in anti-human globulin (AHG) tests: optimum conditions and quality control.

Replicate blind AHG tests with weak IgG anti-D sensitised red cells revealed that 32% of workers caused 5 per cent or more false negative errors by using excessive agitation in reading techniques. The common quality control procedure of adding strongly sensitised cells to all negative AHG tests cannot reveal this type of error. Furthermore, strongly sensitised control cells may create an illusion of safety because AHG giving a false negative test with weak antibody in a serum sample may still show a reassuringly strong positive in the control test. "In-house" assessment of all staff and automatic cell-washers by blind replicate tests is recommended as an effective way of improving AHG test performance, thus reducing many of the errors involving false negative AHG tests seen year after year in External Proficiency Trials.

Antibodies↗
PubMed1986

A human-human monoclonal anti-D by direct fusion with a lymphoblastoid line.

The human lymphoblastoid cell line W1-L2-729-HF2 has been fused with B cells from a plasmaphoresed anti-D donor immunized with D+ cells. A stable monoclonal antibody-producing cell line has been produced which yields culture supernatant of good titre without the need for concentration. The production and use of this reagent as an alternative Rh D typing reagent for use by saline and enzyme manual tests and automated tests in a Technicon 16C machine is discussed. Du red cells are detected in enzyme enhanced tests.

Antibodies, Anti-Idiotypic↗
PubMed1985

Differing reactions of monoclonal anti-A antibodies with oligosaccharides related to blood group A.

Inhibition radioimmunoassays with blood group A-related oligosaccharides have been used to investigate the specificities of six monoclonal anti-A antibodies, three of which had been intentionally generated by immunization of mice with blood group A erythrocytes and A-active blood group substance, and three were incidentally produced following immunization of mice with human tonsil cell membranes or a human colon cancer cell line. By hemagglutination, these antibodies are highly specific for human blood group A erythrocytes. However, they differ from one another in their reaction patterns with mono- and difucosyl A antigen structures and the corresponding afucosyl sequences on Type 1 and Type 2 backbone structures. The six antibodies, together with four previously characterized anti-A monoclonal antibodies (originally raised against the receptor for epidermal growth factor) have been classified into five groups. The first two groups consist of antibodies with broad specificities for A-related structures. There are five antibodies in the first group (TL5, 29.1, A17/3D1, MH2/6D4, and MH1/5D1) reacting to varying degrees with the mono- and difucosyl A antigen structures on either type of backbone sequence. In the second group are two antibodies (A15/3D4 and A15/3D3) which are difficult to inhibit with the oligosaccharides tested, but they reacted best with monofucosyl A structure on either type of backbone. Each of the remaining three antibodies had a distinct and more restricted reaction pattern, with a specificity for the difucosyl A antigen on both types of backbone (antibody EGR/G49) or the Type 1-based mono- and difucosyl A antigen structures (antibody MAS 016c) or the Type 2-based monofucosyl A antigen structure (antibody 455). The reactions of four of the antibodies with N-acetylgalactosamine or with oligosaccharides containing the afucosyl sequence GalNAc alpha 1-3Gal suggest that they may react with certain glycoconjugates with alpha-N-acetylgalactosaminyl termini ("A-like" structures) that are unrelated to the products of the blood group A gene-specified alpha-N-acetylgalactosaminyl-transferase. Knowledge of the differing reactions of these monoclonal antibodies is important for interpreting their reactions with glycoproteins and glycolipids of diverse origins.

ABO Blood-Group System↗
PubMed1984

A new monoclonal anti-A. Culture supernatants with the performance of hyperimmune human reagents.

By proper selection for good growth and high avidity, we have prepared a new anti-A monoclonal antibody producing cell line that gives culture supernatants as potent as US-licensed commercial hyperimmune human reagents and which meet USA FDA standards without the need for concentration. The production and use of this reagent is cost effective and makes it a candidate to replace conventional anti-A typing reagents.

ABO Blood-Group System↗