CHARACTERISTICS OF BONE-MARROW AND BLOOD-CELLS IN HUMAN-LEUKEMIA THAT PRODUCE LEUKEMIA INHIBITORY ACTIVITY (LIA)

Cells in the bone marrow and blood of patients with acute and chronic myeloid and lymphoid leukemia which produce leukemia inhibitory activity (LIA) specific for normal granulocyte-macrophage progenitor cells (CFU-c) have been characterized as belonging to the third population of lymphoid-like cells which are neither T nor B but which have Fe receptors. The cells are non-adherent, non-phagocytic, of low density (<1.070 g/cm3), slowly sedimenting (2-6 mm/h) and present in the sheep red blood cell rosetting populations which are E-, EAC-, Ig-, EA+, and are Ia- as determined by a complement cytotoxicity test using rabbit anti-human Ia-like antibody. The LIA-producing cell has been further characterized by its response to certain agents with known immunoregulatory activity. Bacterial lipopolysaccharide, tuberculin purified protein derivative, Bacillus Calmette-Guérin, dextran sulphate and pokeweed mitogen suppressed the production of LIA. Total suppression of LIA production by LPS required the constant presence of this agent; but hydrocortisone and dexamethasone abrogated LPS suppression of LIA production. LIA could not be found in normal human adult bone marrow and blood cells or fetal bone marrow, spleen, or liver cells. Further evidence for the specificity of LIA action was obtained since LIA did not inhibit erythropoietin dependent human erythroid progenitor cell (BFU-e, CFU-e) proliferation. © 1979.