B cells are a vital part of the adaptive humoral immune system. They are distinguished from other lymphocytes by the B Cell Receptor (BCR) that allows the binding of specific antigens. Generated in adult bone marrow and following maturation, B cells are activated by antigen recognition and a signal from T helper cells or the antigen itself. They produce antibodies and act as antigen-presenting cells. They can develop into memory B cells to establish immunological memory or Plasma B cells that secrete large quantities of antibodies. Each stage of B cell development and differentiation requires multiple transcription factors and cell surface proteins.