Innate Response Activator (IRA) B Cells Reside in Human Tonsils and Internalize Bacteria In Vitro

• Published in: PloS one Vol. 10; no. 6; p. e0129879
• Main Authors: Chiappini, Nico, Cantisani, Rocco, Pancotto, Laura, Ruggiero, Paolo, Rosa, Domenico, Manetti, Andrea, Romano, Antonio, Montagnani, Francesca, Bertholet, Sylvie, Castellino, Flora, Del Giudice, Giuseppe
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.06.2015; Public Library of Science (PLoS)
• Subjects: Adolescent; Antigens, CD19 - genetics; Antigens, CD19 - metabolism; Antigens, CD20 - genetics; Antigens, CD20 - metabolism; B cells; B-Lymphocytes - immunology; B-Lymphocytes - microbiology; Bacteria; CD19 antigen; CD20 antigen; CD5 antigen; CD5 Antigens - genetics; CD5 Antigens - metabolism; Cell activation; Cells, Cultured; Child; Colony-stimulating factor; Confocal microscopy; Cytometry; Effector cells; Flow cytometry; Follicles; Granulocyte-macrophage colony-stimulating factor; Granulocyte-Macrophage Colony-Stimulating Factor - genetics; Granulocyte-Macrophage Colony-Stimulating Factor - metabolism; Health aspects; Humans; Immune response; Immune system; Immunoglobulin D; Immunoglobulin M; Infection; Infections; Localization; Lymphocytes; Lymphocytes B; Macrophages; Microscopy; Palatine Tonsil - cytology; Palatine Tonsil - immunology; Palatine Tonsil - microbiology; Phagocytes; Phagocytosis; Respiratory tract; Spleen; Staphylococcus aureus - pathogenicity; Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0129879

Innate response activator (IRA) B cells have been described in mice as a subset of B-1a B cells that produce granulocyte/macrophage colony-stimulating factor (GM-CSF) and have been found in the spleen upon activation. In humans, identification, tissue localization and functionality of these lymphocytes are poorly understood. We hypothesized that IRA B cells could reside in human palatine tonsils, which are a first line of defense from infection of the upper respiratory tract. In the present work, we used flow cytometry and confocal microscopy to identify and characterize human IRA (hIRA) B cells in tonsils. We show that CD19⁺CD20⁺GM-CSF⁺ B cells are present in the tonsils of all the subjects studied at a frequency ranging between ~0.2% and ~0.4% of the conventional CD19⁺CD20⁺GM-CSF⁻ B cells. These cells reside within the B cell follicles, are mostly IgM⁺IgD⁺, express CD5 and show phagocytic activity. Our results support a role for hIRA B cells in the effector immune response to infections in tonsils.