William J. Mawby

Incomplete glycosylation of erythrocyte membrane proteins in congenital dyserythropoietic anaemia Type II (CDA II)

The alterations in the erythrocyte membrane proteins of individuals with congenital dyserythropoietic anaemia (CDA II) were studied. Alterations were observed in both the erythrocyte sialoglycoproteins and erythrocyte anion transport protein (Band 3). There was a decrease in the apparent molecular weight of the major sialoglycoprotein α (glycophorin A) as well as a general reduction in the intensity of staining of all the sialoglycoproteins by the PAS stain. Sialoglycoprotein α isolated from CDA II erythrocytes contained 30% less sialic acid than normal α. The anion transport protein of CDA II erythrocytes migrated as a band with a lower molecular weight than the normal protein on SDS‐gel electrophoresis. The CDA II anion transport protein had a substantially reduced content of N‐acetylglucosamine and galactose, which probably reflects a reduction in the number of N‐acetyl‐lactosamine units carried by the protein. Our results suggest that there is a general defect in glycosylation of the major membrane glycoproteins of CDA II erythrocytes. We suggest that this glycosylation defect is a consequence of bone marrow stress.

A NOVEL HYBRID SIALOGLYCOPROTEIN IN Sta POSITIVE HUMAN ERYTHROCYTES

Human erythrocytes expressing the rare blood group MNSs‐related antigen Sta (Stones) have an abnormal hybrid sialoglycoprotein designated (δ‐α)Sta. The abnormal (δ‐α)Sta sialoglycoprotein probably results from chromosomal misalignment with unequal crossing over between the α and δ genes in a manner analogous to that which gives rise to the anti‐Lepore‐type haemoglobins.

Reactivity with erythroid and non-erythroid tissues of a murine monoclonal antibody to a synthetic peptide having amino acid sequence common to cytoplasmic domain of human glycophorins C and D

Three synthetic peptides encompassing the entire cytoplasmic polypeptide sequence (amino acid residues 82‐128) of glycophorin C (GPC) and glycophorin D (GPD) were used to immunize mice for the production of monoclonal antibodies (MoAbs). Only the synthetic peptide (GPC‐peptidel) corresponding to C‐terminal residues 112‐128 elicited a MoAb (named BGRL‐100) which could react with native and denatured GPC and GPD. We characterized BGRL‐100 by inhibition using GPC‐peptide 1 and red cell sialoglycoproteins. The ability of BGRL‐100 to interact with native GPC and GPD was assessed by immunoprecipitation with normal red cells (RBCs), and with denatured GPC and GPD by Western blotting of both normal RBCs and RBCs carrying GPC variants. Immunohistochemical staining of human tissue sections was performed using both BGRL‐100 and a rat MoAb (named BRAC‐1), which is specific for an extracellular domain of GPC and GPD. Both antibodies showed strong staining of erythroid lineage haemopoietic cells in fetal liver, sinusoids of adult liver and RBCs in the blood vessels of all tissues tested. Neither antibody reacted with epithelia from a range of human tissues. However, both MoAbs stained neural tissue in a distinctive fibrillar pattern. This suggests the presence of an analogue of erythroid GPC in neural tissues.