Heterogenous expression of decay accelerating factor and CD59/membrane attack complex inhibition factor on paroxysmal nocturnal haemoglobinuria (PNH) erythrocytes

In order to clarify the characterization of phenotypes of paroxysmal nocturnal haemoglobinuria (PNH) erythrocytes (E), we analysed the expression of decay accelerating factor (DAF) and CD59/membrane attack complex inhibition factor (MACIF) on the membrane surface of PNH-E by means of the flow cytometric method using anti-DAF and/or CD59/MACIF monoclonal antibodies in nine PNH-patients. In two-colour analysis, this expression of PNH-E was classified into three fractions; negative, intermediate and positive according to intensity. The negative fraction was classified into two groups; one group an exclusively negative population, and the other a negative population having slightly DAF-positive E. The intermediate fraction was recognized on PNH-E of cases with PNH II-E and extremely heterogenous. In the positive fraction, this expression was almost the same as on normal E except for case 8. In single-colour analysis for DAF or CD59/MACIF, three fractions were classified as well as the definition in two-colour analysis. In single-colour analysis, the expression on PNH-E was also heterogenous in each fraction and among PNH-patients. However, the intermediate fraction for CD59/MACIF was not found on PNH-E of cases without PNH II-E, although intermediate fraction for DAF was recognized on PNH-E of some cases with PNH III-E in addition to those with PNH II-E. The results suggest that expression of CD59/MACIF and DAF on the membrane surface of PNH-E phenotypes is heterogenous and varies among PNH patients.