title: Surrogate light chain-mediated interaction of a soluble pre-B cell receptor with adherent cell lines.
abstract: Signals initiated by the precursor B cell receptor (pre-BCR) are critical for B cell progenitors to mature into precursor B cells. The pre-BCR consists of a homodimer of microH chains, the covalently associated surrogate L (SL) chain composed of VpreB and lambda5, and the transmembrane signal molecules Ig(alpha) and Igbeta. One way to explain how maturation signals are initiated in late progenitor B cells is that the pre-BCR is transported to the cell surface and interacts from there with a ligand on stroma cells. To address this hypothesis, we first produced soluble Fab-like pre-BCR and BCR fragments, as well as SL chain, in baculovirus-infected insect cells. Flow cytometry revealed that, in contrast to Fab-like BCR fragments, the soluble pre-BCR binds to the surface of stroma and several other adherent cell lines, but not to B and T lymphoid suspension cells. The specific binding of the soluble pre-BCR to stroma cells is saturable, sensitive to trypsin digestion, and not dependent on bivalent cations. The binding of pre-BCR seems to be independent of the H chain of IgM (microH chain), because SL chain alone was able to interact with stroma cells. Finally, soluble pre-BCR specifically precipitated a 135-kDa protein from ST2 cells. These findings not only demonstrate for the first time the capacity of a pre-BCR to specifically bind to a structure on the surface of adherent cells, but also suggest that the pre-BCR interacts via its SL chain with a putative ligand on stroma cells.
authors.affiliation: Division of Molecular Immunology, Department of Internal Medicine III, Nikolaus-Fiebiger Center, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Bradl
authors.forename: H M
authors.initials: HM
authors.lastname: Jäck
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D002469:Cell Separation; D002474:Cell-Free System / Q000276:immunology / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D007140:Immunoglobulin Fab Fragments / Q000096:biosynthesis / Q000235:genetics; D007147:Immunoglobulin Light Chains / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054444:Immunoglobulin Light Chains, Surrogate; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000276:immunology / Q000378:metabolism; D054420:Pre-B Cell Receptors; D011233:Precipitin Tests; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012995:Solubility; D017154:Stromal Cells / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D007140:Immunoglobulin Fab Fragments; D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D010455:Peptides; D054420:Pre-B Cell Receptors; D011947:Receptors, Antigen, B-Cell; D011994:Recombinant Proteins