Human normoblast A antigen seen by immunoelectron microscopy

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.

Absence of ABH antigens on neutrophils

Many investigators have concluded that polymorphonuclear leucocytes (PMN) express ABH antigens in parallel to red cells (RBC). We have examined human PMN for ABH antigens using human isoantibodies and mouse monoclonal antibodies with three highly sensitive and specific two-stage assay systems: fluorescence flow cytometry, immunofluorescence microscopy, and avidin-biotin immunoperoxidase microscopy. In all three assays the ABH antigens could not be detected on the surface of PMN. Previous reports alleging that ABH antigens occur on PMN probably represent false positive reactions due to inherent technical problems.

Transplantation of major ABO-incompatible bone marrow depleted of red cells by hydroxyethyl starch

23 bone marrow transplant recipients whose donors where major ABO-incompatible received marrow depleted of red cells prior to infusion utilizing gravity sedimentation in hydroxyethyl starch. The in vitro red cell-depletion procedure effectively removed 97.8% (mean) of the red cells from the harvested marrows and preserved 86.8% of the nucleated cells and 98.2% of the CFU-C activity in 25.4% of the original volume. All recipients had a significant quantity of isohemagglutinins of both IgM and IgG classes demonstrable in their serum at the time of the marrow infusion. Patients were premedicated and well-hydrated prior to the infusion and tolerated the infusion well. These patients demonstrated bone marrow engraftment at the same rate as did those patients whose marrow donors were either ABO-identical or minor ABO-incompatible. There was no difference in the incidence of or time to development of graft versus host disease, the incidence of graft rejection, or patient survival among the groups. Recipients of red cell-depleted major ABO-incompatible bone marrow transplants demonstrated production of donor-type red cells somewhat later and required slightly more red cell transfusion support that did the other groups of recipients. This red cell-depletion technique is safe and effective in the management of major ABO-incompatible bone marrow transplantation.

Zwa antigen distribution on the human platelet: an electron microscope study using a colloidal gold labelled marker

We present the application of a new technique for visualizing surface antigen distribution patterns on intact platelets, treated with anti Zwa antibody, using colloidal gold labelled anti-human immunoglobulin as a marker. Platelets from Zwa negative and from both heterozygous and homozygous Zwa positive individuals were examined for surface Zwa antigen distribution. Platelets fixed with paraformaldehyde show an even distribution of gold particles with a well-developed reticular pattern over their surfaces. Platelets heterozygous for Zwa shows considerable antigen variation, some platelets having similar quantities of antigen to, others much less than, homozygotes. The importance of platelet fixation prior to antigen demonstration by anti Zwa antibody and immunogold visualization is seen by the redistribution of antigen on unfixed platelets. It is suggested that this technique could be exploited to investigate the relationship between platelet surface antigens or structures and their functions.

Blood group A antigen site distribution and immunoglobulin binding in relation to red cell age

Heterogeneity of alpha antigen site density was demonstrated on individual human A1 and A2 type red cells by immunoelectronmicroscopy using haemocyanin-conjugated antiglobulin. Examination of red cells fractionated on a Percoll density gradient showed that the heterogeneity was not age-related. The presence of autologous immunoglobulin on senescent red cells was also confirmed by the same technique.

Uranyl-labelled antibody (ULA) method and its application for Rh antibodies

The existent labelling materials for studies of antigen--antibody interaction at ultrastructural level, namely ferritin and peroxidase, because of their large molecular size do not fulfill all requirements of excellent markers for electron microscopy (EM). Uranyl acetate has a molecule 354 times smaller than IgG and its uranium atom is electron-dense. These physical characteristics of uranyl acetate make it a labelling material par excellence as described in this article. Quantitative and qualitative studies of Rh antigen-antibody interactions are for the first time presented at the ultrastructural level, and the application of the uranyl-labelled antibody (ULA) method for weak antisera (dilutions 100 to 1000 time higher than the Coombs range of sensitivity) is demonstrated. The ULA method opens a new era for studies of antigens, antibodies and their interactions because it will demonstrate visibly details of the antigen-antibody interaction and is especially suitable for studies of weak antisera.

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.