Immune Lysis of AET-treated Normal Red Cells (PNH-like Cells)

NORMAL human red cells treated with the sulphydryl compounds AET (2-aminoethylisothiouronium bromide) or cysteine in suitable conditions develop some of the characters of the red cells of paroxysmal nocturnal haemoglobinuria (PNH) 1 . In particular, they lyse in slightly acidified fresh compatible normal serum ( p H. 6.5) Mengel et al. 2 later reported that they had obtained similar results by incubating normal red cells with another sulphydryl compound, reduced glutathione. Lysis in acidified serum (a positive Ham test) has been considered characteristic of PNH, and appears to be an expression of the peculiar sensitivity of such cells to lysis by complement. This has been investigated with a complement lysis sensitivity test based on the use of red cells sensitized with a constant, optimal amount of an anti-I antibody and then treated with graded amounts of fresh compatible normal human serum as a source of complement PNH cells were found to consist of two populations, one markedly sensitive to lysis by C′ (about twenty-five times more sensitive than normal cells) and the other usually only slightly more (about twice) sensitive than normal cells. The very sensitive population of cells and the existence of two populations of cells are distinguishing characteristics of PNH which have not so far been found in health or in any other disease state.