Hasan, Md Mahmudul

Abstract Although IL-10–producing regulatory B cells (Bregs) play important roles in immune regulation, their surface phenotypes and functional characteristics have not been fully investigated. In this study, we report that the frequency of IL-10–producing Bregs in human peripheral blood, spleens, and tonsils is similar, but they display heterogenous surface phenotypes. Nonetheless, CD24hiCD38hi transitional B cells (TBs) and CD24hiCD27+ B cells (human equivalent of murine B10 cells) are the major IL-10–producing B cells. They both suppress CD4+ T cell proliferation as well as IFN-γ/IL-17 expression. However, CD24hiCD27+ B cells were more efficient than TBs at suppressing CD4+ T cell proliferation and IFN-γ/IL-17 expression, whereas they both coexpress IL-10 and TNF-α. TGF-β1 and granzyme B expression were also enriched within CD24hiCD27+ B cells, when compared with TBs. Additionally, CD24hiCD27+ B cells expressed increased levels of surface integrins (CD11a, CD11b, α1, α4, and β1) and CD39 (an ecto-ATPase), suggesting that the in vivo mechanisms of action of the two Breg subsets are not the same. Lastly, we also report that liver allograft recipients with plasma cell hepatitis had significant decreases of both Breg subsets.

AbstractBackgroundIL‐10‐producing regulatory B cells (Bregs) are widely ascribed immune regulatory functions. However, Breg subsets in human asthma have not been fully investigated.ObjectiveWe studied Breg subsets in adult allergic asthma patients by assessing two major parameters, frequency and IL‐10 expression. We then investigated factors that affect these two parameters in patients.MethodsPeripheral blood mononuclear cells (PBMCs) of adult allergic asthma patients (N = 26) and non‐asthmatic controls (N = 28) were used to assess the frequency of five subsets of transitional B cells (TBs), three subsets of CD24highCD27+ B cells and B1 cells. In addition to clinical data, IL‐10 expression by individual Breg subsets was assessed by flow cytometry.ResultsAsthma patients had decreases of CD5+ and CD1d+CD5+, but an increase of CD27+ TBs which was significant in patients with moderate asthma (60 < FEV1 < 80). Regardless of asthma severity, there was no significant alteration in the frequencies of 6 other Breg subsets tested. However, we found that oral corticosteroid (OCS) significantly affected the frequency of Bregs in Breg subset‐specific manners. OCS decreased CD5+ and CD1d+CD5+ TBs, but increased CD27+ TBs and CD10+CD24highCD27+ cells. Furthermore, OCS decreased IL‐10 expression by CD27+ TBs, all 3 CD24highCD27+ B cell subsets (CD5+, CD10+ and CD1d+) and B1 cells. OCS‐mediated inhibition of IL‐10 expression was not observed in the other Breg subsets tested.Conclusion & Clinical RelevanceAlterations in the frequency of Bregs and their ability to express IL‐10 are Breg subset‐specific. OCS treatment significantly affects the frequency as well as their ability to express IL‐10 in Breg subset‐specific manners.