Summary
We have studied the effect of IgG, IgA, IgM, lambda light chains, Fc fragments, heat-aggregated gammaglobulin, albumin and fibrinogen on the interaction of latex, Kaolin, celite or bentonite particles with human platelet-rich plasma.
1. Marked enhancement of platelet aggregating activity was produced by preincubating these particles with IgG at an appropriate concentration. Excess IgG abolished this platelet aggregating property.
2. Platelet aggregation could also be induced by betamethasone acetate particles. The latter and IgG-coated latex, Kaolin or bentonite particles were inhibited by chymotrypsin substrates and inhibitors.
3. Heat-aggregated IgG produced platelet aggregation in platelet-rich plasma only when adsorbed onto (Kaolin) particles.
4. Results obtained with fibrinogen-coated Kaolin suggest that the particles thus acquired a slightly increased platelet clumping activity.
5. The other proteins studied failed to enhance the platelet aggregating activity of Kaolin particles, and could even inhibit the formation of IgG-coated Kaolin particles able to readily aggregate platelets.
