Characterization of the erythropoietic progenitor cells (BFU-E) in paroxysmal nocturnal haemoglobinuria (PNH).

In order to investigate erythropoiesis in paroxysmal nocturnal haemoglobinuria (PNH), the relative proportions of complement-mediated lysed erythroblasts in individual bursts of two cases of PNH were analysed by a modified complement lysis sensitivity test using the trypan blue dye exclusion method. All bursts contained both complement-sensitive and complement-insensitive erythroblasts and the ratio between them varied from burst to burst. The means +/- SD of the haemolytic percentages of individual bursts in cases 1 and 2 were 30.9 +/- 10.8% (n = 20, ranging from 13.2% to 52.8%) and 54.8 +/- 16.4% (n = 31, ranging from 26.4% to 82.5%), respectively. In addition, the cumulative frequency distributions of the proportions of complement-mediated lysed erythroblasts in individual bursts approached normal frequency distributions. These results suggest that two red cell populations with different susceptibilities to complement in PNH are derived from a single population of erythropoietic progenitor cells rather than a dual population of normal and PNH erythropoietic progenitor cells.