Table 1.

Comparison between homotypic and heterotypic aggregation

	Homotypic aggregation	Heterotypic aggregation
Localization	Confined to the vascular wall	Detectable in peripheral blood
Platelet activation required	Not under high shear rate	Yes
Mechanism of stabilization	Multiple ligand-receptor interactions with thrombogenic surface (demonstrated)	Multiple ligand-receptor interactions with leucocyte membrane (hypothesized)
Main effector molecule(s)	Varies depending on haemodynamic condition and lesion components	P-selectin, P-selectin glycoprotein ligand-1
Platelet release reaction	Required for irreversible stabilization, mainly mediated by dense granule contents	Required for initiation, mediated by alpha granule contents