Platelet-bound C3, C9, and CD40L. Washed platelets (from EDTA tubes) from patients 1 (♦), 2 (▴), 3 (●),4 (◇), or controls (○) were incubated with chicken anti-human C3 antibody, goat anti-human C9 antibody, or rabbit anti-human CD40L; binding was detected on patient platelets, but less on control platelets. No serum was added in these experiments. Results for patients 1 and 2 and controls (n = 10) were carried out twice with reproducible results. Results for patients 3 and 4 were carried out once.