Differential expression of endoglin on fetal and adult hematopoietic cells in human bone marrow.
Endoglin, a glycoprotein that is expressed by human endothelial cells, binds TGF-beta 1 and -beta 3 with high affinity. It was originally identified with the 44G4 mAb that was produced against a human pre-B cell line. We now report that another anti-pre-B cell mAb, 29-G8, reacts with pro-B and pre-B leukemic cells, but not with mature B and T cells, and recognizes a different epitope of endoglin. The 29-G8 mAb bound specifically to recombinant endoglin and immunoprecipitated a phosphorylated homodimeric glycoprotein with subunits of M(r) 95,000 from the 697 pre-B cell line. This new Ab removed all of the molecules identified by the prototypic 44G4 anti-endoglin Ab, but the reverse was not true. A subpopulation of 29-G8+ endoglin molecules on this pre-B cell line was unreactive with the 44G4 mAb, thus suggesting that these anti-endoglin Abs see different epitopes that may discriminate different species of endoglin molecules. Flow cytometric analysis with the 29-G8 mAb revealed two endoglin-positive subpopulations in fetal bone marrow: early B-lineage precursor cells (CD19+ and CD34+), and proerythroblasts (CD71+ and glycophorin A+). In adult bone marrow, only the proerythroblast subpopulation was observed. Stromal cells derived from fetal bone marrow also reacted strongly with the 29-G8 and 44G4 Abs, and these cells responded with enhanced proliferation after stimulation with either TGF-beta 1 or the anti-endoglin Abs. Thus, endoglin, a specialized component of the TGF-beta receptor system, may play a physiologic role in the stromal-hemopoietic cell interactions occurring during development.
Rokhlin
O W
OW
Department of Medicine, University of Alabama at Birmingham 35294, USA.
Cohen
M B
MB
Kubagawa
H
H
Letarte
M
M
Cooper
M D
MD
D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD; D001402:B-Lymphocytes / Q000737:chemistry; D001853:Bone Marrow / Q000196:embryology*; D001854:Bone Marrow Cells; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D000071063:Endoglin; D005333:Fetus / Q000737:chemistry; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000737:chemistry*; D006801:Humans; D006825:Hybridomas; D007124:Immunoenzyme Techniques; D008562:Membrane Glycoproteins / Q000032:analysis*; D011956:Receptors, Cell Surface; D017154:Stromal Cells / Q000737:chemistry; D019010:Vascular Cell Adhesion Molecule-1
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D019010:Vascular Cell Adhesion Molecule-1