Evidence for Stem Cells in the Peripheral Blood of Mice

Leukocytes from the peripheral blood of normal F₁ hybrid mice have been successfully used to promote survival of lethally irradiated parent and closely related homologous animals. Identification of donor-type red cells and leukocytes has been established on samples of blood taken from several long-term survivors. Histologic data and serologic typing of cells from lymph nodes, bone marrow, and spleens of chimeras killed early after irradiation and treatment established that injected peripheral leukocytes had transplanted and were proliferating into lymphocytes, granulocytes, and erythrocytes. Fe⁵⁹ was taken up by red cells and spleens of leukocyte-injected mice but not by tissues of radiation control animals. The newly formed, Fe⁵⁹-labeled erythrocytes were hemolyzed by immune serum specific for donor-type antigens.