title: Stromal cells attract B-cell progenitors to promote B-cell-B-cell contact and maturation.
abstract: The in vitro differentiation of B-lineage progenitors into Ig-secreting mature B cells has classically required a co-culture system containing lipopolysaccharide (LPS) and stromal cells. We have previously showed that B-lineage progenitors cultured in round-bottomed wells can mature and secrete immunoglobulin M (IgM) on par with cultures containing stromal cells. This clearly demonstrates that any factors essential for progenitor cell maturation can be found in cultures containing media, serum, LPS and B-cell progenitors. However, stromal cells are important for the maturation observed when cells are cultured in flat-bottomed wells. We hypothesized that stromal cells may attract B-cell progenitors and promote contacts between responsive cells, a phenomenon that is mimicked by the cultures in round-bottomed wells. In this study, we explore how stromal cells accomplish these functions. We show that stromal cells attract B-cell progenitors in a pertussis toxin-sensitive manner. The stromal cell line S17 produces the chemokine CXCL12, which is able to induce the chemotaxis of B-lineage progenitors. Chemotaxis can be blocked by a small peptide inhibitor (T134) of CXCR4, the CXCL12 receptor. Further, disrupting chemotaxis can reduce the supportive role played by S17 when B-lineage progenitors are cultured in flat-bottomed wells.
authors.affiliation: Ontario Cancer Institute, University Health Network, Department of Immunology, University of Toronto, Toronto, ON, Canada. craig.milne@utoronto.ca
authors.forename: C D
authors.initials: CD
authors.lastname: Milne
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: C J
authors.initials: CJ
authors.lastname: Paige
mesh_terms: D000818:Animals; D016175:B-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology*; D002448:Cell Adhesion / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology*; D018920:Coculture Techniques / Q000266:history*; D005260:Female; D049673:History, 20th Century; D051379:Mice; D008810:Mice, Inbred C57BL; D013234:Stem Cells / Q000166:cytology* / Q000276:immunology*; D017154:Stromal Cells / Q000276:immunology; D013557:Switzerland