LAUSR

Platelets patrol blood vessels where they play an essential role in hemostasis and act as early responders to microbial threats. Billions of them are produced by megakaryocytes (MKs) each day. While the bone marrow was generally regarded as the principal site of platelet production by MKs, pioneering in -vestigations, 1 which were later confirmed by intravital imaging approaches, 2 identified the lungs as an important site of throm -bopoeisis. In a recent study published in the Journal of Clinical Investigation 3 Valet and coworkers show that sites of mega -karyopoiesis, as well as quality of platelet production, change in disease. The dissemination of microorganisms and toxins in blood may ini tiate an overwhelming inflammatory response called sepsis. Sepsis is life threatening and impacts patients even in the convalescent phase of the disease. 4 Drastic changes in platelet numbers, partic ularly thrombocytopenia, and enhanced extramedullary hemato poiesis, for example in the spleen, are recognized in inflammatory conditions. Valet reported substantially increased splenic megakaryopoiesis in sepsis. Moreover, the authors demonstrate that post- sepsis, platelets originating from these splenic MKs bear immu nomodulatory functions, which reduced mortality in a