Myelopeptides (MP) are regulatory molecules produced by animal and human bone marrow cells. A highly purified MP fraction has been isolated from supernatant of the porcine bone marrow cell culture by gel chromatography on Sephadex G-25 and HPLC. MP correct defective antibody response to SRBC in MRL/lpr mice with spontaneous autoimmune disease and increase hemoglobin level in Wv/Wv mice with congenital anemia. Hemoglobin enhancement in Wv/Wv mice is connected with MP influence of differentiation and proliferation of hemopoietic stem cells. MP correction of immunological parameters in MRL/lpr mice resulted in 2-fold prolongation of their life span.