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

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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 structure2–4. 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 induction8,9. 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.