Regulatory B cells in infection, inflammation, and autoimmunity

[Display omitted] •Breg cells are functionally different B cell type.•Breg cells have CD19CD5CD1d combination markers.•It is also determined by CD24hiCD38hi combination.•Breg family also includes LAG-3+CD138hi cells.•Breg cells are activated by TLR agonists.•Breg cells produce IL10 and IL35.•Breg cells cause immunosuppression. Regulatory B (Breg) cells are characterized by differential expression of CD5 and CD1d in mouse and CD24 and CD38 in human immune systems. The Breg family also includes LAG-3+CD138hi plasma cells, CD1d CD5 CD21 CD23 cells, Tim1, PD-L1, PD-L2, CD200- expressing B cells, and CD39hiKi67+ cells originating from the transitional, marginal zone or germinal centre of the spleen. Breg cells produce IL10 and IL35 and to cause immunosuppression. These cells respond to TLR2, TLR4, and TLR9 agonists, CD40 ligands, IL12p35 and heat shock proteins. Emerging evidence suggests that TLR signalling component Myd88 impacts the modulation of Breg cell responses and the host’s susceptibility to infection. Breg cells are found to reduce relapsing-remitting experimental autoimmune encephalomyelitis. However, the Breg-mediated mechanism used to control T cell-mediated immune responses is still unclear. Here, we review the existing literature to find gaps in the current knowledge and to build a pathway to further research.