title: Characterization of the cells in myeloid leukemia that produce leukemia associated inhibitor (LAI) and demonstration of LAI-producing cells in normal bone marrow.
abstract: LAI (leukemia associated inhibitor) is a high mol. wt glycoprotein that reversibly reduces the proliferative rate of normal granulopoietic stem cells but not of clonogenic cells in leukemia. LAI was originally found to be produced and released by cells in acute and chronic leukemia and may play a role in the suppression of normal hematopoiesis in these diseases. We now report the physical and functional characteristics of LAI-producing cells in myeloid leukemia; they have a medium density with peaks in the range of 1.075-1.080 g/ml in continuous Percoll gradients, they are large cells with a sedimentation velocity of about 13-15 mm/h and they are non-phagocytic, non-adherent, non-T, non-B, Fc-receptor positive cells and about equally distributed among C'-receptor positive and negative cells. Normal bone marrow was shown to contain LAI-producing cells present in the non-phagocytic Fc-receptor positive compartment of cells within the density range 1.075-1.080 g/ml. Presented data suggest that LAI-producing cells comprise a subpopulation of cells that may be involved in the regulation of normal granulopoiesis as well as in the suppression of normal hematopoiesis in leukemia. These data also show that LAI-producing cells are different from the cells producing another inhibitor (LIA) recently identified as acidic isoferritins.
mesh_terms: D001853:Bone Marrow / Q000502:physiology*; D002462:Cell Membrane / Q000032:analysis; D002469:Cell Separation; D003114:Colony-Forming Units Assay; D003115:Colony-Stimulating Factors / Q000037:antagonists & inhibitors* / Q000302:isolation & purification / Q000502:physiology; D005293:Ferritins; D006412:Hematopoietic Stem Cells / Q000276:immunology / Q000502:physiology*; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis; D007951:Leukemia, Myeloid / Q000503:physiopathology*; D012016:Reference Values
chemical_list: D003115:Colony-Stimulating Factors; D007136:Immunoglobulins; C020391:acidic isoferritin; D005293:Ferritins