An agonist murine monoclonal antibody to the human c-Mpl receptor stimulates megakaryocytopoiesis

Blood. 1998 Sep 15;92(6):1981-8.

Abstract

Thrombopoietin (TPO) is a hematopoietic growth factor that stimulates megakaryocytopoiesis and platelet production in vivo and promotes the development of identifiable megakaryocytes in vitro. We have developed a murine monoclonal antibody, BAH-1, raised against human megakaryocytic cells, which specifically recognizes the c-Mpl receptor and shows agonist activity by stimulating megakaryocytopoiesis in vitro. BAH-1 antibody specifically binds to platelets and to recombinant c-Mpl with high affinity. Similar to TPO, BAH-1 alone supported the formation of colony-forming unit-megakaryocyte (CFU-MK) colonies. The combination of BAH-1 plus interleukin-3 or of BAH-1 plus human TPO significantly increased the number of human CFU-MK colonies. In addition, BAH-1 monoclonal antibody stimulated the proliferation and maturation of primary bone marrow megakaryocytes in a dynamic heterogeneous liquid culture system. Individual large megakaryocytes as well as small megakaryocytic cells were observed in cultures of CD34(+) CD41(+) cells in the presence of BAH-1 antibodies. Similar to TPO, BAH-1 antibody induced a significant response of murine immature megakaryocytes as observed by an increase in the detectable numbers of acetylcholinesterase-positive megakaryocytes. No effects of BAH-1 antibody were observed on colony-forming unit-granulocyte-macrophage, burst-forming unit-erythroid, or colony-forming unit-erythroid colonies. In vivo studies showed that BAH-1, alone or in combination with TPO, expands the numbers of megakaryocytic progenitor cells in myelosuppressed mice. This antibody should prove useful in understanding the structure-function aspects of the c-Mpl receptor as well as in evaluating the effects of the sustained activation of this receptor in preclinical models of severe thrombocytopenia.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / pharmacology*
  • Antibodies, Monoclonal / physiology
  • Bone Marrow / drug effects
  • Bone Marrow / immunology
  • Colony-Forming Units Assay
  • Female
  • Hematopoiesis / drug effects
  • Hematopoiesis / immunology*
  • Humans
  • Megakaryocytes / drug effects
  • Megakaryocytes / immunology*
  • Mice
  • Mice, Inbred BALB C
  • Neoplasm Proteins*
  • Proto-Oncogene Proteins / agonists*
  • Proto-Oncogene Proteins / immunology*
  • Proto-Oncogene Proteins / pharmacology
  • Receptors, Cytokine*
  • Receptors, Thrombopoietin
  • Thrombopoietin / metabolism*
  • Thrombopoietin / pharmacology

Substances

  • Antibodies, Monoclonal
  • Neoplasm Proteins
  • Proto-Oncogene Proteins
  • Receptors, Cytokine
  • Receptors, Thrombopoietin
  • MPL protein, human
  • Thrombopoietin