Erythrocytes from patients with paroxysmal nocturnal hemoglobinuria are deficient in decay-accelerating factor (DAF), a factor called C8- binding protein or homologous restriction factor, acetylcholinesterase (AchE), and lymphocyte function-associated antigen 3 (LFA-3). These proteins share a common feature that glycan-inositolphospholipid anchors the protein to the membrane, suggesting that an abnormality related to this glycolipid causes multiple protein deficiencies. The relationship between the DAF, AchE, and LFA-3 defects was studied by fluorescent flow cytometric analysis. In five patients, DAF-negative erythrocytes were also AchE-negative. In three patients, a fraction of DAF-negative erythrocytes expressed subnormal levels of AchE, indicating that AchE was synthesized in these DAF-negative cells. Erythrocytes from the patients having DAF-negative, AchE-positive cells were separated according to density and analyzed for expression of DAF and AchE. Both proteins decreased with increase of cell density, suggesting that DAF-negative, AchE-positive cells become AchE-negative during erythrocyte maturation by losing AchE. A low level of LFA-3 was found on DAF-negative erythrocytes from one patient and decreased with erythrocyte maturation. These results support an idea that complete deficiency of glycan-inositolphospholipid-anchored proteins on erythrocytes could result from abnormally early termination of surface recruitment of these proteins, and subsequent dilution through cell divisions and loss from the surface.

This content is only available as a PDF.