Electron microscope study of PNH red cells and AET-treated normal red cells (PNH-like cells).

The morphology of red cells damaged by 2-aminoethylisothiouronium bromide (AET) has been compared to that of PNH cells by transmission and scanning electron microscopy. The main features of the effect of AET as demonstrated by the scanning electron microscope were spherical and deformed cells, with surface craters and relatively large pits. The transmission electron microscope revealed loss of surface structure, an unusual amount of irregularly shaped electrondense material and fine pits in the cell membranes. The paroxysmal nocturnal haemoglobinuria cells showed, by transmission electron microscope, electron-dense material scattered over the cell and fine pitting; by scanning electron microscope, larger craters were seen and swellings protruded from the cell surface. Although the AET changes were not identical with the natural abnormality of paroxysmal nocturnal haemoglobinuria, the two types of cells were sufficiently similar to each other to support the proposition that AET cells have many of the characteristics of paroxysmal nocturnal haemoglobinuria.