To determine whether the production of endogenous APRIL contributes to the megakaryopoiesis process, CD34+ cells isolated from bone marrow patients with ET (with and without JAK2 (V617F) mutation) were grown in MK culture in the presence of soluble human recombinant TACI:Fc fusion protein, which neutralizes APRIL activity [15]. Here, JAK2 is linked to essential thrombocythemia.