[REGULATORY B CELLS]

B lymphocytes represent a major component of the immune system. In addition to their best understood functions, B cells have also been demonstrated to downregulate inflammatory reactions and induce tolerance. The general concept that B cells might have the ability to induce tolerance was already introduced in the 1970s. In mice subpopulations, regulatory B cells and their precursors seem to be able to arise from different subpopulations of Br1 and Br2 cells. In contrast to the murine studies, there is a paucity of data regarding regulatory B cells in healthy people or in patients with autoimmune disease, but such data exists. The composition of regulatory B cells is similar to that of regulatory T cells. In analogy to regulatory T cells, which can be subdivided into Treg, Tr1 and Th3 according to their expression of FoxP3, IL-10 and transforming growth factor TGF-β, respectively, it is proposed to classify human regulatory B cells into Breg, Br1(10) and Br3. Regulatory T and B cells function at different time points. Br1 may be involved in the initiation of pathological responses and Tregs in their maintenance and progression. The main functions of regulatory B cells are mediated by releasing immunosuppressive cytokines and inducing target cell apoptosis. IL-10 is the hallmark cytokine of regulatory B cells. Impaired regulatory capacity of these cells might play a role in the development of inflammatory diseases. Their released cytokines have a broad range of target cells. Therefore, they downregulate the proinflammatory functions of both innate and adaptive immune cells. Targeting B regulatory cells for therapeutic applications holds great promise for the future treatment of autoimmune and allergic inflammatory conditions.