The Role of Membrane Bound Complement in the Aggregation of Mammalian Platelets by Collagen

It has been observed in dogs decomplemented with purified Cobra Venom Factor, that their platelets lose the ability to aggregate in response to collagen stimulation. Further investigation of the effect of CVF in vitro in man, dog and rabbit, and in vivo in dog, reveals that in each case CVF abolishes the collagen response of platelets, and that this effect is dose related. Resuspension of CVF inactivated platelets in plasma containing complement, results in a total return of sensitivity to collagen. Examination of CVF inactivated platelets with the electron microscope, fails to show any marked difference from control platelets. Serotonin granules are still present and the platelets retain a discoid appearance. Incubation of platelets with antibodies to Cl, C3 and C5, results in inhibition of the collagen response, this effect also being dose related. Light microscopy studies indicate that CVF does not affect the adhesion of platelets to collagen but appears to prevent subsequent aggregation. It is suggested that the complement system is involved in the induction of release by collagen, and that inhibition by CVF and anti-complement antibodies is the result of a blocking of the release reaction.

 

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