Administration of recombinant interleukin 2 to mice enhances production of hemopoietic and natural killer cells.

Seven days of continuous perfusion of mice with human recombinant interleukin 2 (rIL 2) (approximately 3 X 10(4) U/day) increased the percentage of large mononuclear leukocytes (LML) among bone marrow, spleen, lymph node cells and liver interstitial cells (LIC). An increase in the lymphokine-activated killer (LAK) activity was evident in these organs. The greatest increase in the number of LML and in the LAK activity was observed among the liver interstitial cells (about 500-fold increase). The LML were nonphagocytic, Thy-1+, sIg-, Ly 2+, L3T4- and asialo Gm1+. Perfusion of athymic nude mice, or of thymectomized, irradiated radiation chimera, showed that the Thy-1+, LAK+ LML were the thymus and T lymphocyte-independent progeny of Thy-1- marrow precursors. The LML had no T cell function in a graft-vs.-host reactivity assay, neither did they have an inhibitory effect on T lymphocyte function in vivo. rIL 2 perfusion did not significantly affect the medullary hemopoiesis but did strongly enhance the extramedullary hemopoiesis, particularly within the interstice of the liver: the number of erythroid and myeloid cell was increased as well as the number of colony-forming units per spleen and colony-forming units per culture for various lineages (20-50-fold increment). These results show that in vivo, rIL 2 has a global enhancing effect on hemopoiesis together with a more selective influence on the production of LML.