title: Macrophages control the retention and trafficking of B lymphocytes in the splenic marginal zone.
abstract: The marginal zone of the spleen is a precisely ordered region that contains specialized subsets of B lymphocytes and macrophages. Disruption of the negative signaling inositol phosphatase, SH2-containing inositol-5-phosphatase 1 (SHIP), results in the loss of marginal zone B cells (MZBs) with reorganization of marginal zone macrophages (MZMOs) to the red pulp of the spleen. This primary macrophage defect, as revealed by selectively depleting SHIP in myeloid cells shows that MZMOs are specifically required for the retention of MZBs. The MZMO phenotype was reverted in SHIP/Bruton's tyrosine kinase (Btk) double knockout mice, thus identifying the Btk activating pathway as an essential component being regulated by SHIP. Furthermore, we identified a direct interaction between the MARCO scavenger receptor on MZMOs and MZBs. Activation or disruption of this interaction results in MZB migration to the follicle. The migration of the MZMOs was further studied after the response to Staphylococcus aureus, which induced MZMOs to move into the red pulp while MZBs migrated into the follicular zone. The marginal zone is therefore a dynamic structure in which retention and trafficking of B cells requires specific macrophage-B cell interactions.
authors.affiliation: Laboratory of Molecular Genetics and Immunology, The Rockefeller University, Box 98, 1230 York Avenue, New York, NY 10021, USA.
authors.forename: Mikael C I
authors.initials: MC
authors.lastname: Karlsson
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Guinamard
authors.forename: Silvia
authors.initials: S
authors.lastname: Bolland
authors.forename: Marko
authors.initials: M
authors.lastname: Sankala
authors.forename: Ralph M
authors.initials: RM
authors.lastname: Steinman
authors.forename: Jeffrey V
authors.initials: JV
authors.lastname: Ravetch
mesh_terms: D000818:Animals; D016175:B-Lymphocyte Subsets / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D005434:Flow Cytometry; D008264:Macrophages / Q000166:cytology / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D023421:Models, Animal; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000172:deficiency / Q000235:genetics / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology*
chemical_list: D010744:Phosphoric Monoester Hydrolases; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases