What growth factor is produced in the kidney and induces growth and differentiation of committed megakaryocyte progenitors?

The correct answer is the growth factor known as TPO, or thrombopoietin. This crucial protein is primarily produced in the liver and kidneys and plays a significant role in hematopoiesis, particularly in the production and regulation of platelets. TPO specifically stimulates the growth and differentiation of committed megakaryocyte progenitors, which are precursor cells that develop into megakaryocytes—the cells responsible for the production of platelets.

TPO binds to its receptor, c-MPL, stimulating megakaryocyte proliferation and maturation, leading to increased platelet production. The significance of TPO in both the development and maintenance of megakaryocyte populations highlights its essential function in hemostasis and the overall maintenance of normal platelet levels in the bloodstream.

Other options listed, such as IL-3, IL-6, and IL-11, do have important roles in hematopoiesis as well, but they do not specifically target megakaryocyte progenitors in the same manner as TPO. For example, IL-3 is a cytokine that supports the proliferation of various blood cell lineages, while IL-6 is primarily associated with the immune response and the acute phase of inflammation. IL-11 is involved in promoting the growth