Effects of deficiencies of glycophorins C and D on the physical properties of the red cell.

Red cells of the rare Leach phenotype lack the membrane glycophorins C and D, and a proportion of the red cells are elliptocytes. Judging from tests on suspensions of red cell ghosts sheared rotationally in an ektacytometer, it has previously been suggested that these membranes are relatively fragile and poorly deformable. We have carried out analyses of individual red cells to investigate possible factors which underlie the physical changes in these glycophorin-deficient cells. Micropipette analysis of the red cell membrane showed that the rigidity and viscosity were normal, both for elliptocytes and discocytes, for three donors deficient in glycophorins C and D. Red cell transit times through 5 microns pores, measured electronically for 2000 individual cells, showed no differences from controls. It was confirmed that the index of deformation obtained using an ektacytometer was reduced, but our results suggest that this arises from shape rather than membrane changes. The elliptocytes were found to have a lower volume and surface area than discocytes from the same donor (measured by micropipette aspiration of single red cells), and were rarely found in less dense red cell fractions. No reticulocytes were found to be elliptical. These data suggest that the elliptocytes are older red cells, and are formed from red cells which are initially released into the circulation with normal shape. Their elongated shape might arise from permanent distortion of the unstable membrane by shear forces in the circulation.