IL1R1 and Thrombocytopenia: The reduction in cell cycle activation was comparable to the one observed in germ-line deleted Il1r1–/– mice (Fig. 3e, f), supporting that Lepr+ CBM-PV cells are the main cells involved in IL-1R-dependent activation of Vwf+ HSCs in response to anti-GPIbα-induced thrombocytopenia.