IL-6 as a Mediator of Platelet Hyper-Responsiveness.

Interleukin-6 (IL-6) is a pleiotropic cytokine with critical roles in immune regulation, inflammation, and haematopoiesis. While its functions in host defence and tissue repair are well established, accumulating evidence suggests that IL-6 also can directly and indirectly modulate megakaryocyte and platelet biology. This review examines the mechanistic basis supporting IL-6-mediated platelet hyper-responsiveness, in addition to its effect on megakaryopoiesis and thrombopoiesis in thromboinflammatory disease states. We discuss how IL-6-mediated trans-signalling may sensitizes platelets to activation, and that this may be exclusive to glycoprotein VI (GPVI) stimulation due to Janus kinase (JAK)-signal transducer 2 crosstalk, in addition to other mechanisms that may contribute to priming platelets. We further highlight clinical evidence linking IL-6 to thrombotic complications in cardiovascular disease and infection (e.g., COVID-19 and sepsis). Given the emerging interest in IL-6-targeting therapies as anti-inflammatory and anti-thrombotic agents, a thorough understanding of how IL-6 can drive platelet responsiveness is crucial.