title: The human lung fibroblast cell line, MRC-5, produces multiple factors involved with megakaryocytopoiesis.
abstract: The human lung fibroblast cell line MRC-5 constitutively produces a megakaryocyte potentiator activity, identified in murine bone marrow liquid culture assays for acetylcholinesterase and megakaryocyte colony assays in the presence of low concentrations of IL-3. The production levels of this activity were increased after stimulation with the phorbol ester analog, mezerein, and the calcium ionophore, A23187. Complete purification of a protein having this activity from conditioned media of induced MRC-5 cells was achieved using gel filtration and ion exchange chromatography. The first 14 residues of the purified protein identified by amino-terminal sequencing were identical to the first 14 residues of IL-6. Recombinant human IL-6 was tested and found to promote megakaryocyte growth. IL-1 beta, another component detected in MRC-5 conditioned media, was unable to promote megakaryocyte colony formation but did reduce the concentration of IL-6 necessary to support megakaryocyte colony formation. Immunoprecipitation using rabbit antiserum prepared against IL-6 removed the megakaryocyte growth activity found in MRC-5 conditioned media. Thus, connective tissue cells such as fibroblasts in the bone marrow may co-stimulate thrombocytopoiesis via IL-6 and, possibly, via IL-1 production.
authors.affiliation: Department of Protein Chemistry, Cetus Corporation, Emeryville, CA 94608.
authors.forename: R
authors.initials: R
authors.lastname: Yamamoto
authors.forename: L S
authors.initials: LS
authors.lastname: Lin
authors.forename: R
authors.initials: R
authors.lastname: Lowe
authors.forename: M K
authors.initials: MK
authors.lastname: Warren
authors.forename: T J
authors.initials: TJ
authors.lastname: White
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis; D000595:Amino Acid Sequence; D001854:Bone Marrow Cells; D002460:Cell Line; D002845:Chromatography; D003114:Colony-Forming Units Assay; D005347:Fibroblasts / Q000502:physiology; D006133:Growth Substances / Q000096:biosynthesis* / Q000302:isolation & purification; D006410:Hematopoiesis; D006801:Humans; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000302:isolation & purification / Q000502:physiology*; D008168:Lung / Q000166:cytology* / Q000502:physiology; D008533:Megakaryocytes; D008969:Molecular Sequence Data
chemical_list: D006133:Growth Substances; D015850:Interleukin-6; D000110:Acetylcholinesterase