title: Phenotypic and Morphological Properties of Germinal Center Dark Zone Cxcl12-Expressing Reticular Cells.
abstract: The germinal center (GC) is divided into a dark zone (DZ) and a light zone (LZ). GC B cells must cycle between these zones to achieve efficient Ab affinity maturation. Follicular dendritic cells (FDCs) are well characterized for their role in supporting B cell Ag encounter in primary follicles and in the GC LZ. However, the properties of stromal cells supporting B cells in the DZ are relatively unexplored. Recent work identified a novel stromal population of Cxcl12-expressing reticular cells (CRCs) in murine GC DZs. In this article, we report that CRCs have diverse morphologies, appearing in open and closed networks, with variable distribution in lymphoid tissue GCs. CRCs are also present in splenic and peripheral lymph node primary follicles. Real-time two-photon microscopy of Peyer's patch GCs demonstrates B cells moving in close association with CRC processes. CRCs are gp38(+) with low to undetectable expression of FDC markers, but CRC-like cells in the DZ are lineage marked, along with FDCs and fibroblastic reticular cells, by CD21-Cre- and Ccl19-Cre-directed fluorescent reporters. In contrast to FDCs, CRCs do not demonstrate dependence on lymphotoxin or TNF for chemokine expression or network morphology. CRC distribution in the DZ does require CXCR4 signaling, which is necessary for GC B cells to access the DZ and likely to interact with CRC processes. Our findings establish CRCs as a major stromal cell type in the GC DZ and suggest that CRCs support critical activities of GC B cells in the DZ niche through Cxcl12 expression and direct cell-cell interactions.
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143;
authors.forename: Lauren B
authors.initials: LB
authors.lastname: Rodda
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143;
authors.forename: Oliver
authors.initials: O
authors.lastname: Bannard
authors.affiliation: Institute of Immunobiology, Kantonsspital St. Gallen, 9007 St. Gallen, Switzerland;
authors.forename: Burkhard
authors.initials: B
authors.lastname: Ludewig
authors.affiliation: Department of Immunobiology and Hematology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan; and Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Kyoto 606-8507, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nagasawa
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143; Jason.Cyster@ucsf.edu.
authors.forename: Jason G
authors.initials: JG
authors.lastname: Cyster
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D002450:Cell Communication / Q000235:genetics / Q000276:immunology; D054415:Chemokine CCL19 / Q000235:genetics / Q000276:immunology; D054377:Chemokine CXCL12 / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology*; D018858:Germinal Center / Q000166:cytology / Q000276:immunology; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D017464:Receptors, Complement 3d / Q000235:genetics / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology
chemical_list: C515461:Ccl19 protein, mouse; D054415:Chemokine CCL19; D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D017464:Receptors, Complement 3d