Colony formation by BM CD34⁺ cells derived from patients with PNH. (A) Bars represent erythroid (▪) and myeloid (□) colony formation by normal volunteers (n = 10) and 4 patients with PNH. (B and C) Flow cytometric analysis of progeny derived from cultures of CD34⁺ cells of a normal volunteer (B) and a patient with PNH (PNH-1; C). Cells were separated from methylcellulose, washed, and stained with MoAbs directed against CD55 and CD59. Log PE fluorescence intensity versus log FITC fluorescence intensity is plotted. Gates were set based on the isotypic controls.