Red blood cell fragility in multiple sclerosis.

The work of Hellem (1960) and of Gaarder, Jonsen, Laland, Hellem, and Owren (1961) has made it clear that red blood cells are a potent source of adenosine diphosphate of consider able importance in determining the adhesiveness of platelets in vitro. Caspary (1965) showed that the presence of even 2% haematocrit red cells was enough to confer a normal degree of stickiness on platelets suspended in plasma. The implication of this finding, brought out in correspondence which followed the publication of the latter paper (Caspary, 1966), is that platelet stickiness might depend in some measure on the readi ness with which erythrocytes yield adenosine diphosphate, and a similar suggestion has more recently been made by Harrison and Mitchell (1966) and Hampton and Mitchell (1966). Atten tion had been drawn to abnormality in size of red blood cells in multiple sclerosis by Plum and Fog (1959), and the present work indicates that they are also more osmotically fragile.