IL-10–producing regulatory B (B10) cells potently suppress allergic diseases, such as contact hypersensitivity (CHS). Splenic B10 cells share overlapping phenotypic markers with CD5+ B1 B cells, CD1dhiCD21+CD23− marginal zone (MZ) B cells, and CD1dhiCD21+CD23+ T2-MZ precursor B cells but do not exclusively belong to either subset.Objective:
In this study we investigated the signaling mechanisms and a novel phenotypic parameter of B10 cells.Method:
We performed microarray analysis comparing IL-10+ and IL-10− B cells. B cell–specific phosphatase and tensin homolog (PTEN)–deficient mice, which exhibit aberrant activation of the phosphatidylinositol 3-kinase (PI3K)–Akt pathway in B cells, were examined.Results:
Microarray analysis revealed that the PI3K-Akt pathway is important for IL-10 production in B cells. PI3K-Akt pathway inhibitors reduced B10 cell numbersin vitro. B10 cell numbers were significantly increased in B cell–specific PTEN-deficient mice. The CHS response was significantly diminished in PTEN-deficient mice. Unexpectedly, splenic B10 cells in these mice were found within the B1 B-cell subset but not within the MZ B-cell subset. In wild-type mice not only MZ B10 cells but also B1-B10 cells were identified in the spleen. In addition, these 2 B10 cell subsets were predominantly found within the CD9+CD80+ B-cell fraction.Conclusion:
A novel splenic B1 regulatory cell subset (B1-B10 cells) was identified. Our findings show that the PI3K-Akt pathway in B cells is critical for B10 cell development and CHS response and that CD9/CD80 coexpression is a novel phenotypic parameter for both MZ-B10 and B1-B10 cells.