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.