The effect of unfractionated heparin, danaparoid, fondaparinux, and argatroban on PF4/anti-PF4 immune complexes from patients with VITT. Heparin and danaparoid inhibit the formation of PF4/ anti-PF4 immune complexes (IC), cause the dissociation of pre-formed ICs, and inhibit platelet activation. Fondaparinux does not inhibit IC formation and does not cause the dissociation of pre-formed ICs, but modestly inhibits platelet activation. Argatroban has no effect on ICs or platelet activation. Professional illustration by Patrick Lane, ScEYEnce Studios.