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B cells are typically characterized by their ability to regulate the immune responses through presenting antigens and producing antibodies. However, a novel B cell subset, named regulatory B cells (Bregs), has been identified. As Tregs, the Bregs are capable of performing both pathogenic and regulatory functions by production of suppressive cytokines, such as IL-10 or TGF-beta1, or by interaction with pathogen T cells or other immune cells. Recent studies indicate that the Bregs play a critical role in the development and resolution of multiple chronic diseases, including inflammatory bowel disease, rheumatoid arthritis, and experimental autoimmune encephalomyelitis. The identification and the clarification of action mechanisms of the Bregs will greatly contribute to understanding the mechanisms of immune tolerance comprehensively and deeply, and to develop the rational therapeutic strategies for arthritis, diabetes, multiple sclerosis, infectious diseases and cancer, etc. In this review, we summarized the recent insights of identification, characterizations, development, and regulation mechanisms of Bregs and these cells' contribution to the pathogenesis of inflammatory diseases.

The interaction of tumor cells with host cells undergoes a progress of immunoediting, including surveillance, equilibrium and escape. The capability of escape from immune-surveillance is a hall marker of tumor cells, which greatly contributes to the tumor growth out of control and the therapy failure in tumor metastasis. It is indicated that tumor cells can recruit amounts of immune cells to tumor site and establish a suppressive immune microenvironment leading to tumor escape. The critical factor for tumor immunotolerance is the establishment of immunosuppressive microenvironment by interaction between pattern recognition receptors with pathogen-associated molecular patterns and damage-associated molecular patterns released from tumor tissue. Therefore, targeting tumor immunotolerance using small molecules or immunostimulatory biological agents such as monoclonal antibody, can inhibit tumor growth and invasion, and subsequently attenuate the tumor metastasis and decrease cancer-caused death.

Molecules of damage-associated molecular patterns (DAMPs) are a class of substances released to intercellular space or peripheral blood by tissues or cells which are stimulated by insults, ischemia or stress. DAMP molecules can be recognized by Toll like receptors, Nod1-like receptors, or Rig-I like receptors and induce autoimmunity or immune tolerance, which play critical roles in various chronic diseases such as arthritis, atherosclerosis, cancer and systemic lupus erythematosus. DAMP molecules include high-mobility group B protein 1, heat shock proteins and S100 proteins etc. The identification of DAMP molecules and clarification of mechanisms of their action will greatly contribute to reveal the pathological mechanisms of chronic diseases and provide a great opportunity to develop the new strategies for the diagnosis, prevention and treatment for these diseases.

Toll-like receptors (TLRs) are widely expressed in the innate and adaptive immune system. They initiate host defense against endogenous and exogenous pathogens containing conserved pathogen associated molecular patterns. TLRs are critical bridges between the innate and adaptive immunity, especially the cellular immunity mediated by T cells. Emerging evidence indicated that B cells express almost all subtypes of TLRs. TLRs play critical role not only in regulation of proliferation, maturation and function of B cells, but also in pathogenesis of diseases, such as systemic lupus erythematosus and chronic lymphocytic leukemia. Targeting TLRs of B cells is a promising therapeutic strategy for these disorders.