title: Adjuvant effect of killed Propionibacterium acnes on mouse peritoneal B-1 lymphocytes and their early phagocyte differentiation.
abstract: B-1 lymphocytes are the predominant cells in mouse peritoneal cavity. They express macrophage and lymphocyte markers and are divided into B-1a, B-1b and B-1c subtypes. The role of B-1 cells is not completely clear, but they are responsible for natural IgM production and seem to play a regulatory role. An enriched B-1b cell population can be obtained from non-adherent peritoneal cell cultures, and we have previously demonstrated that these cells undergo differentiation to acquire a mononuclear phagocyte phenotype upon attachment to the substrate in vitro. Nevertheless, the B-1 cell response to antigens or adjuvants has been poorly investigated. Because killed Propionibacterium acnes exhibits immunomodulatory effects on both macrophages and B-2 lymphocytes, we analyzed whether a killed bacterial suspension or its soluble polysaccharide (PS) could modulate the absolute number of peritoneal B-1 cells in BALB/c mice, the activation status of these cells and their ability to differentiate into phagocytes in vitro. In vivo, P. acnes treatment elevated the absolute number of all B-1 subsets, whereas PS only increased B-1c. Moreover, the bacterium increased the number of B-1b cells that were positive for MHC II, TLR2, TLR4, TLR9, IL-4, IL-5 and IL-12, in addition to up-regulating TLR9, CD80 and CD86 expression. PS increased B-1b cell expression of TLR4, TLR9, CD40 and CD86, as well as IL-10 and IL-12 synthesis. Both of the treatments decreased the absolute number of B-1b cells in vitro, suggesting their early differentiation into B-1 cell-derived phagocytes (B-1CDP). We also observed a higher phagocytic activity from the phagocytes that were derived from B-1b cells after P. acnes and PS treatment. The adjuvant effect that P. acnes has on B-1 cells, mainly the B-1b subtype, reinforces the importance of B-1 cells in the innate and adaptive immune responses.
authors.affiliation: Disciplina de Imunologia, Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo-Escola Paulista de Medicina, São Paulo, Brasil.
authors.forename: Juliana Sekeres
authors.initials: JS
authors.lastname: Mussalem
authors.forename: Carla Cristina
authors.initials: CC
authors.lastname: Squaiella-Baptistão
authors.forename: Daniela
authors.initials: D
authors.lastname: Teixeira
authors.forename: Tatiana Mina
authors.initials: TM
authors.lastname: Yendo
authors.forename: Felipe Garutti
authors.initials: FG
authors.lastname: Thies
authors.forename: Ana Flavia
authors.initials: AF
authors.lastname: Popi
authors.forename: Mario
authors.initials: M
authors.lastname: Mariano
authors.forename: Ieda
authors.initials: I
authors.lastname: Longo-Maugéri
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D002454:Cell Differentiation; D016207:Cytokines / Q000378:metabolism; D005260:Female; D016908:Gram-Positive Bacterial Infections / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D007155:Immunologic Factors / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010586:Phagocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D011425:Propionibacterium acnes / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D016207:Cytokines; D007155:Immunologic Factors; D008070:Lipopolysaccharides