Membrane‐bound immunoglobulins and complement components on young and old red cells

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Abstract
In order to characterize changes in membrane-bound Ig and complement components, [human] red cells (RBC) were separated into young and old populations by simple centrifugation. Old RBC had reduced mean corpuscular Hb volume increased mean corpuscular Hb concentration and reduced sialic acid. Using radioactive anti-antiglobulin techniques, old RBC had more IgG, IgM, IgA and C3d [complement component 3d] on their surfaces than did young RBC; there was no increase on old RBC of C3b, factor B, C4b or C5. Similar results were observed with RBC strongly coated with C3d in vivo from a patient with cold agglutinin disease. RBC taken into EDTA, washed thoroughly in saline and then stored for prolonged periods in Alsever''s solution or kept in autologous EDTA plasma, at 4.degree. C, showed no increase in RBC-bound C3d with increase storage time. If, however, blood was taken into citrate-phosphate-dextrose and maintained at 4.degree. C in autologous plasma, a significant increase in RBC-bound C3d was observed in the mixed-cell population with prolonged storage time. Older donor blood units, taken into citrate-phosphate-dextrose and stored at 4.degree. C as packed red cells, showed higher levels of RBC-bound C3d in the mixed-cell population than did units stored for a shorter time. In no case did donor unit RBC give a positive direct antiglobulin test on serologic testing with anti-C3d. The findings complement data already collected on membrane and cytoplasmic changes in aging RBC and may contribute to an understanding of RBC senescence.