Membrane differentiation in human erythroid cells: Unique profiles of cell surface glycoproteins expressed in erythroblasts in vitro from three ontogenic stages

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Abstract
Human erythroblasts in culture, irrespective of the ontogenic stage of their progenitors, are characterized by: the barely detectable amount of band 3 glycoprotein, the presence of 2 glycoproteins of MW 105,000 and 95,000, the high concentration of glycophorin, and a minimum quantity of the carbohydrate chain susceptible to endo-.beta.-galactosidase (polylactosaminoglycan). Mature erythrocytes, whether of fetal, neonatal or adult origin, are characterized by a high concentration of band 3 glycoprotein, polylactosaminoglycan and glycophorins, but do not contain 105 and 95-kdalton-glycoproteins. The process of erythroid maturation from erythroblasts to erythrocytes is accompanied by the appearance of band 3, the disappearance of 105- and 95-kdalton glycoproteins and a great increase in the quantity of polylactosaminoglycan. The structure of polylactosaminoglycan may not differ between mature erythrocytes and erythroblasts from the same ontogenic stage, but it is distinctively different from 1 stage to the other. The profiles of oligosaccharides released by endo-.beta.-galactosidase and immunofluorescence studies with anti-Ii antibodies indicated that a linear polylactosaminoglycan structure was present in erythroblasts and in erythrocytes of the fetal and newborn stage, whereas a branched polylactosaminoglycan structure was present in erythroblasts and erythrocytes of adult blood. Thus, 2 membrane characteristics are closely associated with the process of erythroid cell development: one , the membrane proteins band 3, band 4.5 and 95- and 105-kdalton glycoproteins, determines the degree of maturation, and the other, polylactosaminoglycan, may determine the ontogenic stage of the erythroblast progenitors.