Demonstration of ferritin-labelled antibodies bound to human erythrocytes fixed with glutaraldehyde

Antibody binding to blood group antigens in relation to temperature: scanning electron microscopy of immunogold-labelled erythrocytes

Binding patterns of mouse monoclonal antibodies (mAb) to P1, Pk, N, I, H, Y or A antigens were visualized in the backscatter electron imaging mode of a scanning electron microscope by indirect immunogold labelling. Experiments were performed at room temperature (RT) and at 4 degrees C. In experiments with anti-P1 and anti-Pk, clusters of immunolabelling particles dominated the immunolabelling pattern much more at RT than at 4 degrees C. By contrast, no clustering was seen with anti-N, even at RT. Clustering was also observed at RT with anti-I, anti-H and anti-Y, and on some Ax and A3 cells with anti-A, but was much reduced at 4 degrees C. Immunolabelling was stronger at 4 degrees C than at RT with all mAb except anti-N and anti-A. The results indicate that glycolipid blood group antigens are more mobile in the membrane of intact erythrocytes at RT than at 4 degrees C, and that the cells bind more antibodies to such antigens at 4 degrees C than at RT. We suggest that antigen immobilization in the cold will reduce cross-linking of antigens and hence increase the number of antibody molecules needed for epitope saturation, leading to increased binding of antibody in the cold. This may be the main reason for cold-enhanced agglutination with human blood group antibodies.

Binding patterns of monoclonal anti-B, anti-H and anti-(Leb + Y) on erythrocytes, imaged in the scanning electron microscope

Binding patterns of monoclonal IgM anti-B, anti-H and anti-(Leb + Y) antibodies on erythrocytes were visualized in the backscatter electron imaging (BEI) mode of a scanning electron microscope by indirect immunogold labelling. The results were independent of secretor status, supporting the view that type 2 oligosaccharides predominate on erythrocytes. There were considerable cell-to-cell variations of amounts of the antigens, presumably because of differences of antigen development. The amount of H antigens may have been overestimated in previous studies. B and H antigens seemed linked mostly to mobile structures, probably lipid, on the convex parts of the cells and to immobile structures, probably protein, on the concave parts. Y antigens appeared bound to mobile structures also on the concave part of the cell membrane. The results therefore confirm that B oligosaccharides on erythrocytes develop from both lipid- and protein-bound H, but suggest that Y develops mainly from lipid-bound H.

A study of immunogold-labelled blood group A erythrocytes in the scanning electron microscope

This report presents binding patterns on A1, A2, A3, Ax and Ae1 erythrocytes of a monoclonal anti-A (A 003) antibody which reacts predominantly with difucosylated A oligosaccharides, visualized with colloidal gold particles in the backscattered electron imaging mode of a scanning electron microscope. A relatively weak labelling was found on most A1 cells, while the labelling in subgroups A2, A3 and especially Ax appeared relatively stronger. Very few Ae1 cells were labelled. The results emphasize the qualitative uniqueness of A1 and suggest that many Ax cells have high proportions of difucosylated A oligosaccharides. Labelling variations were found between different A3 and Ax traits, and in all subgroups between cells and even between different parts of the cells. No immunolabelling differences were found in relation to secretor status.

Interaction forces between red cells agglutinated by antibody. III. Micromanipulation

In the flow studies described in two previous papers (Tha, S. P., and H. L. Goldsmith, 1986, Biophys. J. 50:1109-1116; Tha, S. P., J. Shuster, and H. L. Goldsmith, 1986, Biophys. J. 50:1117-1126), hydrodynamic forces of the order of 10(-11) N (mu dyn) were applied to measure the force of separation of doublets of hardened, sphered human red blood cells cross-linked by anti-B antibody. The same cell preparation and hyperimmune antiserum has here been used to carry out experiments with micropipet aspiration techniques. One cell of a doublet was aspirated onto a holding pipet, and a second aspiration pipet was brought into proximity of the other cell so that the two pipets and the doublet were colinear. Suction was then raised until the two cells separated. Some doublets were assembled by aspiration of a singlet, bringing a second singlet into apposition with the first, and releasing it from the pipet which was then withdrawn. Cells could be repeatedly assembled and separated. At 3.56% vol/vol antiserum, the mean normal force of separation was 0.45 +/- 0.11 nN in phosphate-buffered saline suspensions containing 2.5 x 10(4) cells/microliter; at 1.22% vol/vol antiserum, the value was 0.22 +/- 0.11 nN. The above values of the force were approximately 2.5 x greater than those from the flow studies. The data could be fitted to a Poisson distribution with 0.05 nN as the force needed to break a single cross-bridge (c.f. 0.024 nN from the previous hydrodynamic data). The forces of separation of randomly assembled doublets were lower than those of preexisting doublets. Repeated assembly and separation of doublets showed that the cell surfaces are nonuniform in adhesion strength both over the local scale less than 0.25 micron2 and the cell population.

Quantitation of antibody uptake on A group erythrocytes using immunoautoradiography and monoclonal IgM anti-A

The number of antibody molecules on individual erythrocytes was counted in A1, A2, A3 B and A group individuals using immunoautoradiography (IAR) and monoclonal IgM anti-A1. Quantitation was also done for A group pregnant women. The number of antibody molecules on different red cells of an individual varied widely. Gross variations were also noted in cells of different individuals from one and the same group. The mean values of the uptake of the number of antibody molecules showed the following range A1 greater than A2 greater than Ax greater than A3B. When compared to the average for total A1 adults, red cells of pregnant women and newborn infants showed a 10.7% and 19.7% reduction respectively, in antibody uptake. The mean number of antibody molecules per A1 adult red cells was 5.6 +/- 3 X 10(4), while A2 had 0.85 +/- 0.35 X 10(4) molecules, thus showing a significant quantitative variation.

Ferritin-labeling of antibodies by glutaraldehyde. Comparison of conjugates prepared at different antibody: ferritin: glutaraldehyde ratios

Optimal molar ratios of antibody: ferritin: glutaraldehyde for the preparation of antibody-ferritin conjugates were investigated. The reaction volumes and the antibody concentration were held constant in twenty different reaction mixtures. The effect of five different antibody: glutaraldehyde ratios ranging from 1:25 to 1:400 and of four different antibody: ferritin ratios (1:1 to 1:01) on the yield of antibody-ferritin conjugates was tested in one-step reactions. The 20 different conjugates were tested by a newly developed gel precipitation technique, the inverse fused line rocket immunoelectrophoresis and by counting relative numbers of ferritin monomers and oligomers under the electron microscope. High concentrations of glutaraldehyde produced large heterogeneous precipitates as visualized in the gel technique. The relatively highest yield of ferritin-labeled antibodies without larger conjugates was produced by reacting antibodies, ferritin and glutaraldehyde at molar ratios of 1:1:100. The FRT-antibody conjugates produced at these molar ratios were partly abe to precipitate with their respective antigens.

The cellular distribution of erythrocyte and normoblast A1 and A antigens in normal and preleukemic states. An immunoelectron microscopy study

A1 and A alloantigens were visualized on human erythrocytes and normoblasts by immunoelectron microscopy using peroxidase-coupled antibodies. Specimens were obtained from patients with preleukemia and associated antigen weakening, and from individuals with normal antigen values. Cells were fixed by glutaraldehyde and subsequently reacted with antibodies.

The heterogeneity of erythrocyte antigen distribution in human normal phenotypes: an immunoelectron microscopy study

A and A1 antigen were detected on human blood erythrocytes by immunoelectron microscopy using peroxidase-conjugated antibodies. Cells were obtained from various normal A subgroups, including rare weak A phenotypes and infant (cord blood) samples. Erythrocytes were fixed prior to incubation with specific reagents. The detection of surface antigens was carried out by an indirect method involving anti-A and anti-A1 antibodies and conjugated anti-immunoglobulin antibodies. The surface labelling was seen as a diffuse dense layer. Haemperoxidase-like activity resulted in a faint background which did not interfere at the level of ultrathin sections, with surface staining due to exogeneous peroxidase. The most significant finding was the existence, in a given sample, of several populations of cells as revealed by their antibody-binding capacity. The distribution of the various populations varied from one sample to another according to its subgroup. The progressive weakening of phenotype expression which characterizes the various subgroups from A1 to A weak was paralleled by a decreasing number of "antigen rich" cells, which were still detectable in weak phenotypes as a minor population. This study confirms that a given normal phenotype in fact represents a mixture of antigenically different populations of erythrocytes.

Electron microscopic observations on the H antigen sites of human erythrocytes using ferritin antibody conjugates

Using immunoelectron microscopy, the distribution of the H antigen sites on human erythrocytes was observed in 40 samples of adult, newborn and fetal blood of different ABO phenotypes. The attached ferritin particles indicating the H antigen sites conspicuously varied in number from cell to cell in every specimen. The number of H antigen sites per single red cell was estimated on an average for each sample as follows: O, 3 X 10(5); B, 2 X 10(5); A1, 1.5 X 10(5); A1B, 10(5); A2B, 1.5 X 10(5); Ax, 2.5 X 10(5); AxB, 10(5); Bm, 4 X 10(5); Bw(leukemia), 4 X 10(5); O(newborn), 2.5 X 10(5); B(newborn), 3 X 10(5); A1(newborn), 1.5 X 10(5); A1B(newborn), 2 X 10(5); A1B(fetus), 10(5). The cells in each sample were divided into six cell-populatons according to the number of H antigen sites present. The ratios of distribution of such cell populations are compared for all samples.