title: Germinal center dynamics revealed by multiphoton microscopy with a photoactivatable fluorescent reporter.
abstract: The germinal center (GC) reaction produces high-affinity antibodies by random mutation and selective clonal expansion of B cells with high-affinity receptors. The mechanism by which B cells are selected remains unclear, as does the role of the two anatomically defined areas of the GC, light zone (LZ) and dark zone (DZ). We combined a transgenic photoactivatable fluorescent protein tracer with multiphoton laser-scanning microscopy and flow cytometry to examine anatomically defined LZ and DZ B cells and GC selection. We find that B cell division is restricted to the DZ, with a net vector of B cell movement from the DZ to the LZ. The decision to return to the DZ and undergo clonal expansion is controlled by T helper cells in the GC LZ, which discern between LZ B cells based on the amount of antigen captured and presented. Thus, T cell help, and not direct competition for antigen, is the limiting factor in GC selection.
authors.affiliation: Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA.
authors.forename: Gabriel D
authors.initials: GD
authors.lastname: Victora
authors.forename: Tanja A
authors.initials: TA
authors.lastname: Schwickert
authors.forename: David R
authors.initials: DR
authors.lastname: Fooksman
authors.forename: Alice O
authors.initials: AO
authors.lastname: Kamphorst
authors.forename: Michael
authors.initials: M
authors.lastname: Meyer-Hermann
authors.forename: Michael L
authors.initials: ML
authors.lastname: Dustin
authors.forename: Michel C
authors.initials: MC
authors.lastname: Nussenzweig
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology; D005260:Female; D018858:Germinal Center / Q000166:cytology* / Q000276:immunology*; D006801:Humans; D056724:Immunity, Humoral; D008198:Lymph Nodes / Q000166:cytology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000166:cytology
chemical_list: D000941:Antigens