K562 human leukaemic cells express fetal type (i) antigen on different glycoproteins from circulating erythrocytes

Abstract

During the ontogenic change from fetal to adult human erythrocytes, as well as fetal haemoglobin being replaced by adult haemoglobin, the cell-surface antigen i is converted to I (ref. 1). Recently it has been shown that this antigenic change is the conversion of the linear repeating Galβ1→4GlcNacβ1→3 Gal structure to branched Galβ1→4 GlcNacβ1→3(Galβ1→4GlcNacβ1→6)Gal structure^2–4. We have shown that cell-surface labelling followed by endo-β-galactosidase digestion can distinguish these two forms on the cell surface, and that band 3 and band 4.5 are the major carriers for these antigens on mature erythrocytes⁵. Human leukaemic cell line K562, originally isolated from a patient at blast crisis of chronic myelocytic leukaemia⁶, has recently been shown to synthesize glycophorin A⁷, and to be capable of synthesizing haemoglobin upon induction^8,9. I demonstrate here that K562 cells express the fetal type (i) antigen on distinctly different glycoproteins from those of erythrocytes, by the use of cell-surface labelling followed by endo-β-galactosidase digestion or followed by immunoprecipitation with specific antibodies.