Thompson-Snipes, LuAnn

Abstract TIGIT (T cell immunoreceptor with Ig and ITIM domains) is a co-inhibitory receptor, highly expressed by Tregs, and contributes to the suppressive function of Tregs by limiting pro-inflammatory Th1 and Th17 cell responses. Herein, we report that subsets of human regulatory B cells (Bregs) express surface TIGIT and can thus play a critical role in immune regulation. Using data from human B cell surface arrays and RNA-seq, we identified two major TIGIT+ human Bregs subsets, exhibiting CD24hiCD27+CD39hiIgD+IgMhiCD1chi marginal zone (MZ)-like and CD24hiCD27+CD39+IgD−IgM+CD1c+ memory Bregs. We further demonstrated that TIGIT+ Bregs were also capable of suppressing immune responses by their ability to express not only IL-10 and PD-L1, but also granzyme B and TGFb1. In addition, TIGIT+ Bregs can also suppress immune responses by altering dendritic cell functions. In line with these observations, liver allograft recipients with donor-specific alloantibody (DSA) had significantly lower numbers of TIGIT+ Bregs than those without DSA. Moreover, the frequency of TIGIT+ Bregs correlated with that of CD4+CD25+CD127lo Tregs, while it inversely correlated with the frequency of follicular helper T cells. We thus concluded that TIGIT+ Bregs play critical roles in immune regulation in liver allograft recipients.

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.