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Abstract As antigen-presenting cells (APC), B cells exert a variety of immune regulatory functions mainly by presenting antigens, triggering immune response, and producing antibodies for immune regulation. Regulatory B cells (Bregs) are special subpopulations of B cells with immune-regulating or immune-suppressing properties and play a role in peripheral tolerance. Bregs suppress immune response through inhibiting the differentiation of dendritic cells (DCs), suppressing the proliferation of helper T1(TH1) cells and helper T17 (TH17) cells, inducing the differentiation of fork head transcription factor p3 positive regulatory T cells (FoxP3+ Tregs). Different subsets of Bregs have distinct phenotypes and markers. Different subsets of Bregs participate in immune modulation by different ways. The absence or loss of Bregs exacerbates the severity of many disease such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and graft-versus-host-disease (GVHD). Bregs are also involved in tumor immunosuppressive effect and inhibit the antitumor immune process. In this article, we review the research advances of Bregs in autoimmune diseases, GVHD and tumor. Highlights • Previous studies have shown that regulatory B cells play important roles in inflammatory diseases and tumor. • There is no systematic review of the role of regulatory B cells in inflammatory diseases and tumor. • In this paper, the role of regulatory B cells in inflammatory diseases and tumors is systematically reviewed. • This article provides researchers with the latest systematic research of regulatory B cells. [ABSTRACT FROM AUTHOR]

Emerging evidence reveals the controversial role of B cells in antitumor immunity, but the underlying mechanisms have to be explored. Three latest articles published in the issue 521 of Nature in 2015 reconfirmed the puzzling topic and put forward some explanations of how B cells regulate antitumor T-cell responses both positively and negatively. This paper attempts to demonstrate that different B-cell subpopulations have distinct immunological properties and that they are involved in either antitumor responses or immunosuppression. Recent studies supporting the positive and negative roles of B cells in tumor development were summarized comprehensively. Several specific B-cell subpopulations, such as IgG(+), IgA(+), IL-10(+), and regulatory B cells, were described in detail. The mechanisms underlying the controversial B-cell effects were mainly attributed to different B-cell subpopulations, different B-cell-derived cytokines, direct B cell-T cell interaction, different cancer categories, and different malignant stages, and the immunological interaction between B cells and T cells is mediated by dendritic cells. Promising B-cell-based antitumor strategies were proposed and novel B-cell regulators were summarized to present interesting therapeutic targets. Future investigations are needed to make sure that B-cell-based pharmacological strategies benefit cancer immunotherapy substantially. [ABSTRACT FROM AUTHOR]