Use of aerolysin to detect small PNH populations. LD⁻ cells (10,000) were mixed with CD59-expressing CEM cells 1:1 (A), 1:10 (B), 1:100 (C), 1:500 (D), and 1:1,000 (E) and analyzed for expression of CD59 before (solid line) and after (dotted line) 30 minutes of exposure to 1 nmol/L aerolysin.