Deformability of erythrocytes from four patients with different types of glucosephosphate
isomerase (D‐glucose‐6‐phosphate ketoisomerase, GPI) deficiency has been determined
by cell filtration. Young as well as whole erythrocyte populations had a markedly increased
rigidity and an abnormally strong attachment of haemoglobin to the inner surface of isolated
membranes. Acidic environment may enhance membrane rigidity in vitro and also during
passage of the erythrocytes through the spleen. The decrease of deformability at a pH of 6.8 …