Reduction in Surface Charge as an Explanation of the Recognition by Macrophages of Nuclei Expelled From Normoblasts

Abstract

The density and distribution of electric charge on the surface of rabbit bone marrow cells was visualized by electron microscopy after the cell surfaces had been stained with charged colloidal iron particles . Expulsed erythroid nuclei are less negatively charged than any other cell in the bone marrow . They carry from about one-half to one-third of the charge density on the remaining future reticulocyte . The reduction in the surface charge density is already apparent when the nucleus is partially expulsed . Practically no positive charge was found on its surface or on the surface of any other bone marrow cell . The possibility that the reduced negative charge on the surface of expelled erythroid nuclei is one of the means by which the macrophage distinguishes it from other bone marrow cells is discussed .

Endocytic mechanism of macrophages to anionic foreign substances.

“…Seno and others have suggested that macrophages have specific sites to recognize anionic groups on foreign substances, by which macrophages bind the substances to the surface and take them up into the cytoplasm (10,11,16,23,24,26,27). The general somatic cells may not have such binding sites.…”

Cell-type-related segregation of surface galactosyl-containing components at an early developmental stage in hemopoietic bone marrow cells in the rabbit.

“…The results were compared with our previous findings regarding the modulations of surface sialyl residues on the same ceils in rabbit (14,25,31) and in other mammalian species (15).…”

“…specific saccharides (20, 21) and antigenic sites (7,22). Since, in most cell membrane glycoconjugates, sialic acid is attached either to a galactose or to an N-acetylgalactosamine residue (23,24), the masking and unmasking of these constituents are believed to be particularly important in the abovementioned interactions.We have shown previously that the differentiation and maturation of rabbit erythrocytes (RBC) are associated with striking modulations in cell surface sialic acids (14,25). These changes are expressed as a reduction in the density of sialyl residues after successive divisions of erythroid precursors.…”

“…We have shown previously that the differentiation and maturation of rabbit erythrocytes (RBC) are associated with striking modulations in cell surface sialic acids (14,25). These changes are expressed as a reduction in the density of sialyl residues after successive divisions of erythroid precursors.…”

“…For example, the integrity of surface sialic acids and their continuity with respect to the carrier molecule on the cell surface have been linked to the control of the survival of circulating erythrocytes (4--13) and the phagocytosis of extruded erythroid nuclei in most mammals (14,15). In addition, changes in the normal level and/or distribution of surface sialic acid and terminal galactosyl residues have been implicated in the maturation, the release into circulation, and the homing of lymphoid cells (16,17), as well as the turnover of circulating sialoglycoproteins (18) and the pathological expression in certain diseased blood cells (6,19).…”