title: The first-appearance of neutrophils in the human fetal bone marrow cavity.
abstract: We sought to define the time of first-appearance of neutrophils within the developing human bone marrow cavity, and to compare this with the time of appearance of G-CSF and its receptor (G-CSF-R) at that site. We hypothesized that the onset of G-CSF production is an initiation signal for neutrophil production within the marrow cavity, and that therefore G-CSF mRNA and G-CSF protein in the marrow cavity would immediately precede the first-appearance of neutrophils. To test this, we determined the time of first-appearance of neutrophils in the clavicular marrow space using a monoclonal antibody against myeloperoxidase (MPOAb), and then validated these findings by flow cytometric analyses, for neutrophil cell-surface markers, of cells flushed from the marrow cavity. After thus defining the time of first-appearance of neutrophils, specific mRNA transcripts for G-CSF and G-CSF-R were sought from clavicles of varying gestational ages, using RT-PCR, and the presence of these proteins in the clavicles were sought using immunohistochemistry. We observed that; (1) MPO+ cells first appeared in the clavicular marrow cavity between the 10 to 11th weeks post-conception, (2) Flow cytometric analyses confirmed that these MPO+ marrow cells included CD11b+, CD15+ neutrophils, (3) Transcripts for G-CSF and G-CSF-R, and the specific G-CSF and G-CSF-R proteins, were present in the clavicles by 6 weeks post-conception, 4 to 5 weeks before the first-appearance of neutrophils. Thus, neutrophils first appear in the human clavicular marrow at 10-11 weeks post-conception, and G-CSF and G-CSF-R are present in the developing bone rudiment preceding the appearance of neutrophils. It is unclear whether neutrophils arise in the marrow cavity in response to the onset of production of G-CSF or to other initiation signals.
authors: Department of Pediatrics, University of Florida College of Medicine, Gainesville 32607, USA.
authors: W B
authors: WB
authors: Slayton
authors: Y
authors: Y
authors: Li
authors: D A
authors: DA
authors: Calhoun
authors: S E
authors: SE
authors: Juul
authors: J
authors: J
authors: Iturraspe
authors: R C
authors: RC
authors: Braylan
authors: R D
authors: RD
authors: Christensen
mesh_terms: D001853:Bone Marrow / Q000196:embryology*; D001854:Bone Marrow Cells / Q000166:cytology; D018845:CD11 Antigens / Q000032:analysis; D004906:Erythrocyte Count; D005260:Female; D005865:Gestational Age; D016179:Granulocyte Colony-Stimulating Factor / Q000032:analysis / Q000235:genetics; D006410:Hematopoiesis; D006801:Humans; D007150:Immunohistochemistry; D007958:Leukocyte Count; D016256:Lewis X Antigen / Q000032:analysis; D009504:Neutrophils / Q000166:cytology* / Q000276:immunology; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000032:analysis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018845:CD11 Antigens; D016256:Lewis X Antigen; D012333:RNA, Messenger; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D016179:Granulocyte Colony-Stimulating Factor