Plant lectins have been used to probe changes in cell surface characteristics that accompny differentiation in a complete series of chick erythroid cells. Dramatic differences in lectin receptor mobility were observed between the most immature cells of the series, the proerythroblasts, and cells at the next stage of maturation, the erythroblasts. Both concanavalin A and Ricinus communis agglutinin form caps on proerythroblasts, whereas they develop a patchy distribution on erythroblasts. Erythroid cells at later developmental stages show a homogeneous distribution of surface-bound R. communis agglutinin. Concanavalin A also shows a uniform distribution on the cell periphery, but appears to be concentrated in a ring above the perinuclear region of the cell. In addition to changes in mobility of lectin receptors, a large reduction (50-70%) in the number of lectin receptors per cell accompanies maturation of proerythroblasts to erythroblasts. Pretreatment of the cells with neuraminidase results in enhanced binding of R. communis agglutinin to proerythroblasts. The number of additional R. communis agglutinin receptors exposed by enzyme treatment remains relatively constant during subsequent cell maturation.

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