This primary lymphocyte type develops in the bone marrow and circulates in the periphery to provide immune surveillance. B cells recognize antigen via a specific membrane-bound immunoglobulin which acts as a B cell surface receptor (BCR). Activation of the BCR, along with cell surface co-stimulatory molecules including CD19, drives proliferation and development of progeny “plasma” cells that bear and secrete antibodies of identical specificity.
A subset of activated B cells develops into long-lived memory cells, allowing B cells to play a significant role in adaptive immunity. A putative subset of B cells with immune-regulatory function, known as B regulatory (Breg) cells, has been described in humans and in animal models. These cells are able to secrete inhibitory cytokines such as IL-10 and TGF-β, which act to suppress proliferation of CD4+ T cells and to mediate T regulatory (Treg) cell function via the up regulation of transcription factor Foxp3 and the cell surface co-stimulatory molecule CTLA-4. Breg cells have been identified by flow cytometry based on expression of CD25high CD27high CD86high CD1dhigh IL-10high and TGF-βhigh