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Published on: June 13, 2014
Activation-dependent modulation of B lymphocyte migration to chemokines
M Brandes1, D F Legler, B Spoerri
1Theodor-Kocher Institute, University of Bern, 3000 Bern 9, Switzerland.
Insights
Cultured B lymphocytes migrate towards specific chemokines like BCA-1, SLC, ELC, and SDF-1. This migration is enhanced upon activation but does not involve calcium mobilization or changes in key chemokine receptor expression.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- B lymphocytes are crucial for humoral immunity, requiring precise positioning within lymphoid tissues.
- Chemokines are key regulators of leukocyte migration, but their specific roles in B cell homing are not fully elucidated.
Purpose of the Study:
- To investigate the in vitro migration responses of human B lymphocytes to a panel of 27 chemokines.
- To determine the effect of B cell activation on chemokine-induced migration.
- To explore the underlying mechanisms, including calcium mobilization and chemokine receptor expression.
Main Methods:
- Chemotaxis assays using freshly isolated and cultured human peripheral blood or tonsillar B lymphocytes (CD19+).
- Stimulation of B lymphocytes with lipopolysaccharide (LPS) or anti-CD40 plus IL-4.
- Analysis of intracellular calcium ([Ca(2+)](i)) mobilization and chemokine receptor expression (CXCR4, CXCR5, CCR6) via flow cytometry and transcript analysis.
Main Results:
- Cultured B lymphocytes showed significant migration towards BCA-1, SLC, ELC, and SDF-1, but not inflammatory chemokines.
- Activation of B lymphocytes markedly enhanced migration towards these specific chemokines, peaking at 12-36 hours.
- No significant intracellular calcium mobilization was detected, and migration changes did not correlate with CXCR4, CXCR5, or CCR6 expression.
Conclusions:
- Human B lymphocytes exhibit specific migration responses to a subset of 'housekeeping' chemokines, particularly after activation.
- The observed migration is independent of inflammatory chemokines and typical leukocyte calcium signaling pathways.
- Modulation of B cell migration to these chemokines is likely critical for orchestrating humoral immune responses in secondary lymphoid organs.
Abstract:
In this study we have examined the migration responses of human peripheral blood or tonsillar B lymphocytes to a selection of 27 chemokines. Freshly isolated (CD19(+)) B lymphocytes show greatly impaired in vitro chemotaxis which is overcome by overnight culture. The best responses of cultured B lymphocytes were observed with BCA-1, SLC, ELC and SDF-1, reaching 19-26% of total input cells that have migrated, followed by LARC and TECK with 5-10% of migrated cells, whereas no other chemokine was found to be active. Stimulation of B lymphocytes with lipopolysaccharide or anti-CD40 plus IL-4 resulted in marked enhancement of the migration response to BCA-1, SLC, ELC and SDF-1, reaching 30-60% migrated cells at 12 or 36 h of culture respectively. The activation-dependent increase in the migration efficacy was transient and declined to base level responses after 72 h of culture. Under no circumstances did we detect B lymphocyte chemotaxis to inflammatory chemokines. Also, mobilization of intracellular calcium ([Ca(2+)](i)), an otherwise typical response of leukocytes to chemokines, was not observed. The transient increase in B lymphocyte migration did not correlate with changes in chemokine receptor expression, as evidenced by cell surface staining with antibodies to CXCR4, CXCR5 and CCR6, and by receptor transcript analyses. BCA-1, SLC, ELC and SDF-1 are typical 'housekeeping' chemokines with prominent expression at discrete locations in lymphoid tissues. Modulation of migration to these chemokines may be a critical mechanism for the proper positioning of B lymphocytes during humoral responses in secondary lymphoid tissues.
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