RÉSUMÉ
Chronic myelogenous leukemia (CML) is a hematologic malignancy arising from an abnormal hemopoietic stem cell. Our earlier studies have identified defects in spectrin tetramer formation and organization of cytoskeletal proteins (Basu et al., Biochim. Biophys. Acta 1988, 121-126); and decreased ankyrin binding to ankyrin-depleted vesicles in CML patients. These may lead to clustering of band 3 and increased binding of autologous IgG. This has now been explored by studying the binding of 125I-protein A to normal and CML erythrocytes. There is increased binding of 125I-protein A in CML erythrocytes compared to normal erythrocytes. Since binding of autologous IgG is responsible for removal of erythrocytes from the circulation, the above findings suggest that CML erythrocytes are likely to be prematurely removed from the circulation, accounting for anemia.
Sujet(s)
Acide 4,4'-diisothiocyano-stilbène-2,2'-disulfonique , Acide 4-acétamido-4'-isothiocyanato-stilbène-2,2'-disulfonique/analogues et dérivés , Protéine érythrocytaire-1 échangeuse d'anions/composition chimique , Ankyrines , Protéines du sang/métabolisme , Électrophorèse sur gel de polyacrylamide , Membrane érythrocytaire/composition chimique , Humains , Immunoglobuline G/métabolisme , Leucémie myéloïde chronique BCR-ABL positive/sang , Protéines membranaires/métabolisme , Protéine A staphylococcique/métabolisme , Sulfates/métabolismeRÉSUMÉ
Membrane sidedness of human eythrocytes was investigated in inside-out vesicles (IOV's), ghosts and intact cells by means of transmission electron microscopy (e.m.) after tannic acid fixation. No gross difference in appeearance of either membrane surface was observed when IOV's were subjected to conventional e.m. preparation. This included in addition to tannic acid, a double fixation with glutaraldehyde and osmium, followed by "en bloc" and thin section staining with uranyl acetate and lead citrate. By contrast, if IOV's were treated with a high EDTA concentration (2-5 mM) before tannic fixation, granular, electron-dense deposits were found on one of the surfaces. The presence of such a meterial was unaffected by neuraminidase treatment prior to the EDTA step. On the hand, red cells show no electron-dense deposits when exposed to EDTA (5 mM) unless they presented a light cytoplasm and an altered membrane appearance. Such a material was only observed on the inner membrane surface. Furthermore, a similar distribution of such deposits following EDTA treatment was also found in white ghosts before being induced to vesiculate. These results indicate that tannic acid can be employed as a marker for the cytoplasmic surface of the human erythrocyte membrane when used in combination with EDTA