Summary
The effect of white cells on platelet aggregation has been studied. White cells have
little or no effect on nor-adrenaline induced clumping, produce disaggregation of
ADP, 5HT and thrombin induced clumping, and first enhance and then reverse ATP induced
clumping. The effects of white cells on clumping are similar to their effects on the
clumping agents themselves, for they do not inactivate nor-adrenaline, but rapidly
inactivate ADP, and produce a more active agent from ATP. In respect of the patient
to patient variability in clumping activity, the amount of aggregation produced by
ATP is very closely related to the white cell content of the PRCP, whereas the variations
in ADP induced clumping must be due to other factors. The significance of these findings
for the possible role of the platelet clumping agents in arterial thrombosis is discussed.