Adjuvant effect of killed Propionibacterium acnes on mouse peritoneal B-1 lymphocytes and their early phagocyte differentiation

PLoS One. 2012;7(3):e33955. doi: 10.1371/journal.pone.0033955. Epub 2012 Mar 20.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adjuvants, Immunologic / pharmacology*
  • Animals
  • B-Lymphocytes / cytology*
  • B-Lymphocytes / metabolism
  • Cell Differentiation*
  • Cytokines / metabolism
  • Female
  • Gram-Positive Bacterial Infections / immunology
  • Gram-Positive Bacterial Infections / metabolism
  • Gram-Positive Bacterial Infections / pathology
  • Immunologic Factors / pharmacology
  • Lipopolysaccharides / pharmacology
  • Macrophages, Peritoneal / immunology*
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Phagocytes / cytology*
  • Phagocytes / immunology*
  • Phagocytes / metabolism
  • Propionibacterium acnes / immunology*


  • Adjuvants, Immunologic
  • Cytokines
  • Immunologic Factors
  • Lipopolysaccharides