Interleukin 11 (IL-11) is a multifunctional cytokine first isolated in 1990 from bone marrow-derived stromal cells. It is a member of the IL-6-type cytokine family, distinguished based on their use of the common co-receptor gp130. IL-11 is a key regulator of multiple events in hematopoiesis, most notably the stimulation of megakaryocyte maturation. IL-11 has been demonstrated to improve platelet recovery after chemotherapy-induced thrombocytopenia, induce acute phase proteins, modulate antigen-antibody responses, participate in the regulation of bone cell proliferation and differentiation. IL-11 causes bone-resorption. It stimulates the growth of certain lymphocytes and, in the murine model, stimulates an increase in the cortical thickness and strength of long bones. As a signaling molecule, IL-11 has a variety of functions include placentation and to some extent of decidualization. IL-11 has been expressed to have a role during implantation of the blastocyst in the endometrium of the uterus. IL-11 is manufactured using recombinant DNA technology and is marketed as a protein therapeutic called oprelvekin, for the prevention of severe thrombocytopenia in cancer patients.