Modulation of B cell responses by Toll-like receptors.

B lymphocytes are well known because of their key role in mediating humoral immune responses. Upon encounter with antigen and on cognate interaction with T cells, they differentiate into antibody-secreting plasma cells, which are critical for protection against a variety of pathogens. In addition to their antibody-production function, B cells are efficient antigen-presenting cells and express a variety of pathogen recognition receptors (PRRs). Engagement of these PRRs with their respective ligands results in cytokine and chemokine secretion and the upregulation of co-stimulatory molecules. These events constitute innate immune responses. Toll-like receptor (TLR) activation provides a third signal for B cell activation and is essential for optimal antigen-specific antibody responses. In some situations, TLR activation in B cells can result in autoimmunity. The purpose of this review is to provide some insights into the way that TLRs influence innate and adaptive B cell responses.