title: CD9 is a unique marker for marginal zone B cells, B1 cells, and plasma cells in mice.
abstract: Marginal zone (MZ), follicular (FO), and B1 B cells form the long-lived naive B cell compartment. To identify surface markers that define MZ B cells in mice, we generated a panel of mAbs reactive with MZ but not FO B cells. One of these mAbs, MZ3, was found to recognize the tetraspanin CD9. CD9 expression not only distinguishes MZ B cells from FO B cells but also divided peritoneal cavity B1 cells into smaller subsets. After short-term in vitro stimulation with various mitogens, FO B cells failed to induce CD9 protein, while MZ B cells up-regulated the level of CD9 protein. However, after prolonged culture of FO B cells with LPS, surface CD9 was induced, together with syndecan 1, indicative of plasma cell differentiation. Following immunization with a T-independent-2 Ag, R36A, or a T-dependent Ag, SRBC, we found that CD9 is not expressed by germinal center B cells but is eventually expressed on plasma cells in response to both T-independent-2 and T-dependent Ags. Collectively, these results suggest that MZ B cells and B1 cell subsets are the immediate precursors of plasma cells in the primary response and that CD9 is acquired by T-dependent plasma cells.
authors.affiliation: Division of Developmental and Clinical Immunology and Department of Microbiology, University of Alabama, Birmingham, AL 35294, USA.
authors.forename: Woong-Jai
authors.initials: WJ
authors.lastname: Won
authors.forename: John F
authors.initials: JF
authors.lastname: Kearney
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis* / Q000235:genetics; D001402:B-Lymphocytes / Q000737:chemistry* / Q000502:physiology; D015415:Biomarkers; D002454:Cell Differentiation; D002478:Cells, Cultured; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D010950:Plasma Cells / Q000737:chemistry* / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D060245:Tetraspanin 29
chemical_list: D015703:Antigens, CD; D015415:Biomarkers; C554870:Cd9 protein, mouse; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D060245:Tetraspanin 29