title: CD9-regulated adhesion. Anti-CD9 monoclonal antibody induce pre-B cell adhesion to bone marrow fibroblasts through de novo recognition of fibronectin.
abstract: The modulation of adhesive interaction between lymphocyte progenitors and bone marrow stroma may critically determine the maturation and migration of B cell progenitors. mAb against CD9 and beta 1 integrins are reported to induce the homotypic adhesion of pre-B cells. We present evidence that the anti-CD9 mAb 50H.19 and ALB6 but not the proaggregatory anti-VLA-4 mAb 44H6 also enhance the Fc-independent heterotypic adhesion of the human pre-B cell lines NALM-6 and HOON to bone-marrow stromal fibroblasts (BM-FB) but not to bone marrow stroma. CD9-enhanced binding of NALM-6 cells to BM-FB was inhibited 58% by the anti-VLA-4 mAb HP2/1, 36% by the anti-VLA-5 mAb BIIG2, and 99% by their combination. The mAb effectively inhibited adhesion when prebound to NALM-6 cells but not when prebound to BM-FB. The anti-VCAM-1 mAb E1/6 inhibited CD9-enhanced adhesion by only 14% suggesting the involvement of other ligands. Adhesion was inhibited by mAbs against the COOH-terminus and central cell binding domains of fibronectin, as well as by the corresponding CS1 and RGD peptides. Adhesion was not affected by H-7 and sphingosine, inhibitors of protein kinase C. These results suggest that perturbation of CD9 on pre-B cells promotes recognition of stromal cell fibronectin by VLA-4 and VLA-5 and implicates CD9 as a novel regulator of inside-out signaling relevant to B lymphopoiesis.
authors.affiliation: Department of Immunology, University of Alberta, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Masellis-Smith
authors.forename: A R
authors.initials: AR
authors.lastname: Shaw
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015703:Antigens, CD / Q000502:physiology*; D001402:B-Lymphocytes / Q000502:physiology*; D001854:Bone Marrow Cells; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000502:physiology; D002460:Cell Line; D005347:Fibroblasts / Q000166:cytology; D005353:Fibronectins / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D016023:Integrins / Q000032:analysis; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D016029:Receptors, Very Late Antigen / Q000502:physiology; D060245:Tetraspanin 29; D019010:Vascular Cell Adhesion Molecule-1
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C554869:CD9 protein, human; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D016023:Integrins; D008562:Membrane Glycoproteins; D016029:Receptors, Very Late Antigen; D060245:Tetraspanin 29; D019010:Vascular Cell Adhesion Molecule-1