B cells: from early development to regulating allergic diseases

B lymphocytes are characterized by a unique and highly specialized developmental pathway that is responsible for their vast phenotypic and function diversity. B cell development is strictly regulated to ensure sufficient specific humoral immunity while at the same time avoiding any errors that would compromise B cell functionality. The generation and maintenance of mature B cells from the constant flux of bone marrow progenitors is a complex process that is generally poorly understood, although great progress has been made in recent years. B cells have for long been considered mainly as antibody-producing cells and therefore believed to play an important role in the pathophysiology of allergic diseases, primarily through their ability to produce IgE antibodies. However, recent findings have revealed new aspects of their role in immune responses that place them again under the spotlight as important immune regulators, independent of antibody production. This review focuses on the developmental processes responsible for the numerous phenotypes and functions of the B-lymphocyte pool and the different aspects of effector B cell functionality in the context of allergy.