Complement and platelets: Mutual interference in the immune network

•Platelets contain complement factors and bear complement receptors.•Platelets can activate the complement system and vice versa.•Complement and platelets cooperate against pathogens.•Platelets and complement affect autoimmunity and inflammatory disorders.

In recent years, the view of platelets has changed from mere elements of hemostasis to immunological multitaskers. They are connected in manifold ways to other cellular and humoral components of the immune network, one of which is the complement system, a potent player in soluble innate immunity.Our article reviews the crucial and complex interplay between platelets and complement, focusing on mutual regulation of these two interaction partners by their respective molecular mechanisms. Furthermore, the putative relevance of these processes to infectious diseases, inflammatory conditions, and autoimmune disorders, as well as the treatment of patients with biomaterials is highlighted.