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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Human erythroblasts in culture, irrespective of the ontogenic stage of their progenitors, are characterized by: (i) the barely detectable amount of band 3 glycoprotein, (ii) the presence of two glycoproteins with molecular weights 105,000 and 95,000, (iii) the high concentration of glycophorin, and (iv) a minimum quantity of the carbohydrate chain susceptible to endo-β-galactosidase (“polylactosaminoglycan”). In contrast, 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-kilodalton-glycoproteins. Thus, the process of erythroid maturation from erythroblasts to erythrocytes is accompanied by the appearance of band 3, the disappearance of 105- and 95-kilodalton glycoproteins, and a great increase in the quantity of polylactosaminoglycan. The structure of polylactosaminoglycan may not be different between mature erythrocytes and erythroblasts from the same ontogenic stage, but it is distinctively different from one stage to the other. The profiles of oligosaccharides released by endo-β-galactosidase and immunofluorescence studies with anti-Ii antibodies indicated that a linear polylactosaminoglycan structure was present in erythroblasts as well as in erythrocytes of the fetal and newborn stage, whereas a branched polylactosaminoglycan structure was present in erythroblasts as well as erythrocytes of adult blood. Thus, two 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-kilodalton glycoproteins—determines the degree of maturation, and the other—polylactosaminoglycan—may determine the ontogenic stage of the erythroblast progenitors.

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