The Need for Transcription and Translation for Differentiation of Bone Marrow Cells by Thymic Factors in Man

Abstract

The exact mechanism by which the thymus influences differentiation of bone marrow precursor cells into thymocytes after their migration into its environment is not fully understood. Studies in vitro with normal human marrow cells (1, 2) and peripheral blood lymphocytes (PBL) (3) have demonstrated that one or more small populations of cells are inducible to express T cell markers after incubation in the presence of human or calf thymic factors. The molecular nature of the steps induced by these factors prior to the appearance of specific markers on the cell membrane are unknown. In an attempt to elucidate the mode of action of thymic factors on precursor human marrow cells in vitro, we have studied the effect produced by partially purified human thymic factors (HTF) on RNA and protein synthesis in different marrow cell populations, isolated by discontinuous density gradient centrifugation (2). In addition, we have studied the effect of specific inhibitors of RNA and protein synthesis on these events during incubation of the different marrow cell populations with HTF.