Answer to Question 1
Correct Answer: A
Answer to Question 2
Answer: All stages of megakaryocyte development are influenced by TPO including megakaryocyte survival, proliferation, the ploidy level, and the rate of maturation. Stromal cell-derived factor-1 (SDF-1) augments TPO-induced megakaryocyte growth and endothelial adhesion within the marrow microenvironment. TPO also regulates the number of platelets in the peripheral blood. TPO binds to the c-Mpl receptor on platelets in circulation, is internalized, and is degraded to regulate the amount of TPO that can influence platelet progenitors.
Megakaryocyte progenitors proliferate in the presence of IL-3, GM-CSF, stem cell factor, and Flt ligand, whereas megakaryocyte maturation is influenced by IL-6 and
IL-7 (with other cytokines). Transforming growth factor- (TGF-) and -interferon (IFN-) both inhibit megakaryopoiesis.