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Biomedical subjects

A H Merry

Publications and source records attributed to A H Merry.

At least 37 records · Page 2Linked to original sources
PubMed1989

Epitopes on sialoglycoprotein alpha: evidence for heterogeneity in the molecule.

The binding of 15 125I-labelled mouse monoclonal antibodies to cell-surface sialoglycoprotein alpha (SGP alpha: synonym Glycophorin A) was studied using intact IgG and Fab fragments. It was estimated that the number of sialoglycoprotein alpha (SGP alpha) molecules per red cell is of the order of 1 x 10(6) and the number of sialoglycoprotein delta (SGP delta; synonym Glycophorin B) molecules per red cell is of the order of 1.7-2.5 x 10(5). Competitive binding assays showed that antibodies of the same blood group specificity (four anti-Ns reacting with SGP alpha and SGP delta (BRIC 33, BRIC 115, BRIC 120, BRIC 123) and four anti-Wrbs reacting with SGP alpha (R7, BRIC 14, BRIC 89, BRIC 93) inhibited binding of each other to red cells. Two antibodies (R1.3 reacting with SGP alpha and SGP delta and R18 reacting with SGP alpha) recognized distinct epitopes, and the remaining five antibodies (BRIC 116, BRIC 117, BRIC 119, BRIC 127, R10 reacting with SGP alpha) partially inhibited binding of each other to red cells. This latter observation and the finding that four of these antibodies (BRIC 116, BRIC 117, BRIC 119, BRIC 127) bind to a considerably smaller number of antigen sites (1.69-2.71 x 10(5) for intact IgG) than the maximum value obtained, suggests heterogeneity of glycosylation within SGP alpha molecules. The functional affinities of the IgG antibodies ranged from 1 x 10(5) to 4 x 10(7)M-1.

Antibodies, Monoclonal↗
PubMed1989

Inhibition of malarial parasite invasion by monoclonal antibodies against glycophorin A correlates with reduction in red cell membrane deformability.

The effect of well-characterized monoclonal antibodies to red cell surface molecules on the invasion of human red cells by the malarial parasites Plasmodium falciparum and Plasmodium knowlesi was examined. Antibodies to glycophorin A (GP alpha) inhibit invasion for both parasite species, and this is highly correlated with the degree to which they decrease red cell membrane deformability as measured by ektacytometry. This effect on rigidity and invasion was also seen with monovalent Fab fragments. The closer the antibody binding site was to the membrane bilayer, the greater was its effect on inducing membrane rigidity and decreasing parasite invasion. Antibodies to the Wright determinant in particular were the most inhibitory. This differential effect of the various antibodies was not correlated with their binding affinities or the number of sites bound per cell. Antibodies to surface molecules other than GP alpha were without effect. A novel mechanism is described whereby monoclonal antibodies and their Fab fragments directed at determinants on the external surface of red cells might act to inhibit invasion by malarial parasites by altering membrane material properties.

Animals↗
PubMed1988

The chemiluminescent response of human monocytes to red cells sensitized with monoclonal anti-Rh(D) antibodies.

Luminol-enhanced chemiluminescence (CL) was used to assess the metabolic response of human monocytes to red cells sensitized with known amounts of anti-Rh(D). Monoclonal antibodies were used to facilitate a comparison between the functional activities of IgG1 and IgG3 subclasses. The detection of CL provided a simple, rapid and semi-quantitative means of measuring monocyte response to sensitized red cells (IgG-RBC). Monocyte response to IgG3-RBC was quantitatively greater, more rapid and less susceptible to inhibition by fluid phase IgG than monocyte response to IgG1-RBC. The minimum levels of sensitization required to elicit CL from monocytes were approximately 2500 IgG3 molecules per red cell, or approximately 5000 IgG1 molecules per cell.

Antibodies, Monoclonal↗
PubMed1988

Reaction of rheumatoid factors with IgG3 monoclonal anti-Rh(D) antibodies: more frequent reactivity to a monoclonal antibody of the Gm allotype G3m(5) in rheumatoid patients negative for G3m(5).

Human monoclonal anti-Rh(D) antibodies of known IgG isotype and Gm allotype were bound to erythrocytes and then used as the target IgG antigens for rheumatoid factors (RFs) in a direct haemagglutination test. When serum samples from patients with rheumatoid arthritis (RA) were tested for RF specificity towards these IgG monoclonal anti-D antibodies the incidence and titre of reactivity towards an IgG3 monoclonal anti-D antibody was considerably greater than for a polyclonal anti-D antibody of the same Gm allotype, G3m(5). This difference was not explained by the amount of each anti-D antibody which bound to erythrocytes. Furthermore, when patients with RA were divided into groups according to their Gm phenotype, sera from a greater proportion of patients negative for the phenotype G3m(5) reacted to the G3m(5) monoclonal anti-D antibodies than sera from those patients positive for this allotype. Analysis of RF reactivities towards two IgG3 and three IgG1 monoclonal anti-D antibodies, each with different Gm allotypic epitopes, indicated, however, that individual serum samples contained RFs with a spectrum of specificities; some sera appeared to react to a single set of Gm alleles, whereas others also reacted to isotypic or iso-allotypic epitopes, or both. Our data suggest that RFs with specificity for Gm allotypes do not arise in patients who carry that particular allotype owing to tolerance induced in fetal-neonatal life. Conversely, RFs with apparent specificity for a Gm allotype formed in patients negative for that allotype may be reacting to a closely related but different epitope. Final proof requires precise specificities for each RF formed, and IgG3 monoclonal anti-D antibodies would be useful reagents for this purpose.

Antibodies, Monoclonal↗
PubMed1987

Reduced erythrocyte survival following clearance of malarial parasitaemia in Thai patients.

Erythrocyte survival times were measured in healthy Thai controls and in patients following clearance of asexual P. falciparum or P. vivax parasitaemia. In five controls the mean cell life (MCL) of compatible donor erythrocytes was 89.6 d (mean range 73-101 d) compared with a mean MCL of 56.8 d (range 30-66 d) for autologous erythrocytes in 12 falciparum patients. In one of these patients the survival curve was biphasic with a rapid loss of some labelled cells. The survival of compatible donor erythrocytes was also studied in 10 patients and two types of survival curve could be distinguished. In five patients the cells had a mean MCL of 64.4 d (range 42-90 d). In the others survival curves were curvilinear, suggesting a complex mechanism of cell clearance or the presence of more than one cell population. There was initially a more rapid rate of destruction. In P. vivax malaria the MCL of autologous erythrocytes in seven patients was a mean of 67.2 d (range 34-74 d) and that of compatible donor cells in six patients was 66.8 d (range 54-76 d). In all except one of these patients both autologous and donor cell survival curves could be fitted to straight lines. No increase in cell-bound IgG or C3 was evident in 12 patients tested. The differences between the mean MCL in all the groups of patients and the controls were statistically significant at the 5% level. This indicates an increased rate of erythrocyte destruction following clearance of P. falciparum or P. vivax parasites which is not antibody or complement mediated. The mechanism is unknown, but appears to be extrinsic to the erythrocytes themselves and may result from nonspecific activation of the reticuloendothelial function associated with the parasitic infection.

Adult↗
PubMed1987

Monocyte-erythrocyte interaction in autoimmune haemolytic anaemia in relation to the number of erythrocyte-bound IgG molecules and subclass specificity of autoantibodies.

Monocyte-erythrocyte interaction in patients with autoimmune haemolytic anaemia (AIHA) was assessed by phagocytosis and rosette assays. In most patients, a relationship was observed between haemolysis and the phagocytosis of their own erythrocytes by allogenic peripheral monocytes. An evaluation of the number of immunoglobulins on patient erythrocytes and IgG subclasses of autoantibodies shows that in patients with only IgG1 antibody or with additional IgG2 or/and IgG4, phagocytosis was always observed when the number of erythrocyte-bound IgG molecules was above 2,000. On the other hand, in all patients where IgG3 was detectable, phagocytosis was observed even if the amount of IgG was as low as 230 molecules per erythrocyte. Similar observations were made in the rosette assay. Generally, the number of erythrocyte-bound IgG and the presence of phagocytosis were correlated with the degree of haemolysis, but there were exceptions, i.e. the amount of IgG and phagocytosis were high but there was no evidence of haemolysis, or where there was little IgG, no phagocytosis but haemolysis was present. Our data do not indicate that erythrocytes from AIHA are preferentially bound to autologous monocytes.

Anemia, Hemolytic, Autoimmune↗
PubMed1987

Estimation of the number of binding sites for a murine monoclonal anti-Lub on human erythrocytes.

The number of Lub antigen sites on the human erythrocyte membrane, as recognised by the murine monoclonal antibody BRIC-108, has been determined. The number of antibody molecules bound per cell on one example of cells of the phenotype Lu(a-b-) with recessive inheritance was an average of around 200 in replicate determinations, which probably represents non-specific antibody binding. A similar number of antibody molecules to this bound to trypsin- or pronase-treated normal cells or cells of the Lu(a-b-) phenotype associated with the inheritance of the X-borne gene, XS2. The number of binding sites on three examples of cells of the phenotype Lu(a-b-) with dominant inheritance was from 440 to 690. A variation in the number of binding sites per cell from 1,640 to 4,070 was found in five individuals with the phenotype Lu(a-b+) and from 850 to 1,820 in four individuals with the phenotype Lu(a+b+). Four individuals with the Lu(a+b-) phenotype had an average of 480 binding sites per cell. The Lub antigen therefore appears to a have low-site density and a variable level of expression on the erythrocyte surface.

Animals↗
PubMed1987

Phagocytosis of erythrocytes sensitized with known amounts of IgG1 and IgG3 anti-Rh antibodies.

Phagocytosis was investigated using human peripheral monocytes and erythrocytes sensitized with known amounts of subclass-specific IgG anti-Rh antibodies. The erythrocyte-bound IgG was quantitated by a radiometric antiglobulin test. This evaluation revealed the following: (1) there is a relationship between phagocytosis and the number of erythrocyte-bound IgG molecules; (2) phagocytosis is IgG subclass-dependent, since a similar degree of phagocytosis is observed with fewer IgG3 than IgG1 molecules and also the minimum number of IgG3 molecules for phagocytosis is 150-640, whilst for IgG1 the minimum is 1,230-4,020; (3) the minimum levels of sensitization for phagocytosis should be detectable by the serological antiglobulin test; (4) the phagocytosis assay is no more sensitive than the monocyte rosette assay for the detection of anti-Rh alloantibodies, and (5) phagocytosis of adherent erythrocytes observed by video-enhanced microscopy indicated that erythrocytes may adhere to monocytes for a considerable time before phagocytosis, but that phagocytosis itself was rapid.

Erythrocytes↗
PubMed1986

Identification and partial characterization of the human erythrocyte membrane component(s) that express the antigens of the LW blood-group system.

Rhnull human erythrocytes lack the antigens of the Rhesus blood-group system, have an abnormal shape, have an increased osmotic fragility, and are associated with mild chronic haemolytic anaemia. Rhnull erythrocytes also lack all antigens of the LW blood-group system, but the functional significance of this deficiency is unknown. We have identified, by immunoblotting with two mouse monoclonal antibodies (BS46 and BS56), the LW-active component(s) in normal human erythrocytes as a broad band of Mr 37 000-47 000 on SDS/polyacrylamide-gel electrophoresis. Treatment of intact human erythrocytes with endoglycosidase F preparation destroyed the epitopes recognized by antibodies BS46 and BS56, suggesting that one or more N-glycosidically linked oligosaccharides are required for the formation of the LW antigens. Estimation of the number of LW antigen sites per erythrocyte by using radioiodinated purified antibody BS46 gave average values of 4400 molecules/cell for Rh(D)-positive adult erythrocytes and 2835 molecules/cell for Rh(D)-negative adult erythrocytes. Like the Rh(D) polypeptide, the LW polypeptide(s) is (are) associated with the cytoskeleton of normal erythrocytes. These results suggest the possibility that the absence of the LW polypeptide may also contribute to the functional and/or morphological abnormalities of Rhnull erythrocytes.

Acetylglucosaminidase↗
PubMed1986

The use of monoclonal antibodies to quantify the levels of sialoglycoproteins alpha and delta and variant sialoglycoproteins in human erythrocyte membranes.

By using radioiodinated monoclonal antibodies we have estimated that there are about 600 000 copies of sialoglycoprotein alpha (synonym glycophorin A) and 80 000 copies of sialoglycoprotein delta (synonym glycophorin B) per normal human erythrocyte. Erythrocytes expressing the product of only one alpha gene contain about 300 000 copies of alpha/cell. Two erythrocyte types containing alpha-delta hybrid molecules were studied. Those with heterozygous expression of the (alpha-delta)Mi.V gene contain about 100 000 alpha-delta copies per cell, whereas those with heterozygous expression of the En(UK) gene contain about 80 000 alpha-delta copies/cell. Erythrocyte types containing delta-alpha hybrid molecules were also studied. About 200 000 copies of (delta-alpha)Dantu were measured in cells with heterozygous expression of the (delta-alpha)Dantu gene (donor M.P.), whereas about 315 000 copies of the putative (delta-alpha)Dantu hybrid were found on the erythrocytes of donor J.O. [which also have heterozygous expression of the putative (delta-alpha)Dantu gene]. The erythrocytes of donor M.P. have normal levels of alpha, whereas those of donor J.O. have only about half-normal levels. It is proposed that the hybrid sialoglycoprotein of donor J.O. is of alpha-delta-alpha composition [(alpha-delta-alpha)Dantu] rather than delta-alpha and results from a double cross-over analogous to that which gives rise to haemoglobin Parchman.

Antibodies, Monoclonal↗
PubMed1986

Evidence against immune haemolysis in falciparum malaria in Thailand.

Evidence of immune mediated haemolysis was sought in 83 patients with P. falciparum malaria in eastern Thailand. Amongst 73 patients with uncomplicated infection 12 (16.4%) had a weakly positive direct antiglobulin test (DAT). The incidence in 32 children aged 8-16 years was similar to that in adults. Of 10 patients with cerebral malaria, six adults, all of whom were in unrousable coma, had a positive DAT. Erythrocyte-bound IgG1 accounted for the positive DAT in all cases; sensitization with complement or other IgG subclasses was not found. Patients with uncomplicated malaria had a median value of 70 IgG molecules per erythrocyte compared with 65 molecules per cell in 67 healthy controls. This difference was not statistically significant but could account for the lower incidence of a positive DAT in control subjects (4.5%). There was no correlation between the number of IgG molecules per cell and the degree of anaemia during the acute or convalescent phases of the infection. There is no evidence from this study that an immunohaemolytic process contributes to the anaemia of falciparum malaria in eastern Thailand.

Adolescent↗
PubMed1986

Fc receptors for IgG1 and IgG3 on human mononuclear cells--an evaluation with known levels of erythrocyte-bound IgG.

The Fc receptors on mononuclear cells were investigated by a rosette technique in which human erythrocytes were sensitized with a known number of molecules of anti-Rh antibodies (IgG1 or IgG3). The number of IgG molecules was quantitated by a radiometric antiglobulin test. The present quantitative evaluation reveals that (1) there is a logarithmic relationship between the proportion of rosettes and the amount of erythrocyte-bound immunoglobulin for both types of mononuclear cells, and for both subclasses; (2) similar percentage of rosettes can be obtained with fewer IgG3 than IgG1 molecules (about 1:4); (3) for a given number of erythrocyte-bound immunoglobulins a higher percentage of rosettes is observed with monocytes than with lymphocytes (ratios of about 3:1 for IgG1 and 5:1 for IgG3); (4) the minimum number of IgG3 molecules for adherence is 180-460 for monocytes, 520-1,300 for lymphocytes, whilst for IgG1 the numbers are 1,180-4,300 for monocytes and 3,400-14,200 for lymphocytes; (5) the minimum levels of sensitization by alloantibodies for adherence should be detectable by the antiglobulin test.

Autoantibodies↗
PubMed1984

Two individuals with elliptocytic red cells apparently lack three minor erythrocyte membrane sialoglycoproteins.

We have studied the erythrocytes of two individuals (P. L. and K. W.) who lack the Gerbich (Ge) blood-group antigen. The erythrocytes of P. L. and K. W. were not reactive with two monoclonal antibodies (NBTS/BRIC 4 and NBTS/BRIC 10) which reacted with normal erythrocytes. The membranes of P. L. and K. W. erythrocytes appeared to lack three minor sialoglycoproteins (beta, beta 1 and gamma). These three minor sialoglycoproteins were found to be associated with the cytoskeletons of normal erythrocytes. Approx. 10% of the erythrocytes of P. L. and K. W. were frankly elliptocytic. We suggest that one or more of the minor sialoglycoproteins may play a part in maintaining the discoid shape of the human erythrocyte.

Blood Group Antigens↗
PubMed1984

Detection of carotenoids in blood donors taking Orobronze: a cautionary note.

During the summer, plasma samples from eight blood donors at this transfusion centre were found to have a bright orange colour. All donors appeared to be healthy and haematological tests showed no abnormality. Extracts of lipid from the plasma revealed the presence of the carotenoid canthaxanthin and other carotenoid metabolites which were identified by thin-layer chromatography and high-pressure liquid chromatography, light absorbtion and mass spectrometry. On questioning the donors it was found that they had been taking a course of 'Orobronze' (an oral 'bronzing' treatment containing canthaxanthin). Canthaxanthin was still detectable in the plasma several months after the donors had ceased taking the capsules. At present it seems that there would be no deleterious effects on healthy individuals taking orobronze. The full implications of the presence of canthaxanthin in plasma transfused to patients do, however, require further investigation of carotenoid metabolism in man.

Blood Donors↗
PubMed1984

Quantitation of IgG on Erythrocytes: correlation of number of IgG molecules per cell with the strength of the direct and indirect antiglobulin tests.

The number of IgG molecules bound to the erythrocyte surface for a given agglutination score in the antiglobulin test was studied with several different examples of anti-D, anti-E, anti-c, anti-Kell, anti-Fya, anti-Jka and immune anti-A antisera. The serological scores show a significant correlation with the mean values for bound IgG molecules within a restricted range, although the number bound for a given score may vary by up to 20%. The limit of detection was 100-120 IgG molecules per cell and when over 1,000 were bound, the cells were completely agglutinated. Anti-Kell bound under low ionic strength saline conditions required a greater number of molecules for a given agglutination strength. The relatively low levels of bound IgG necessary to give strong agglutination make the direct antiglobulin test (DAT) less valuable for following the progress of auto-immune haemolytic anaemia (AIHA) than a quantitative test. The latter test does not, however, provide any additional information in AIHA cases with a negative DAT as in these the anaemia does not appear to be due simply to the number of bound IgG molecules. Detection of certain antibodies may not be achieved simply by increasing the sensitivity of the antiglobulin test when correctly performed.

Anemia, Hemolytic, Autoimmune↗