On the reactivity of corneal collagen and subcomponent C1q of the complement system with human platelets and IgG-coated latex particles

Collagen was isolated from bovine cornea and tested for reactivity towards platelets and IgG-coated polystyrene latex particles. The corneal collagen caused a dose- and temperature-dependent platelet aggregation in all human platelet-rich plasmas studied. As little as 0 . 31 micrograms of purified corneal collagen could trigger platelet activation. Human C1q, a subcomponent of the first complement component (C1), which shares extensive chemical-structural similarities with collagen, was able to inhibit the platelet aggregation provoked by corneal collagen. This blocking effect could be, however, overcome by increasing collagen doses. In a slide method or in aggregometry both corneal collagen and C1q agglutinated IgG-coated latex particles in a dose-dependent manner. Addition of such latex particles to platelet-rich plasmas or preincubation of the particles with collagen reduced or prevented the platelet action of collagen, suggesting that due to their reactivity with collagen immune complexes may play an inhibitory role in collagen-caused platelet aggregation. The results are discussed in relation to pathological events that lead to collagenolysis and also with respect to wound healing in the injured cornea.