Science, Tech, Math › Science B Cells: Antibody Producing Immune Cells Share Flipboard Email Print Getty Images / CHRISTOPH BURGSTEDT / SCIENCE PHOTO LIBRARY Science Biology Cell Biology Basics Genetics Organisms Anatomy Physiology Botany Ecology Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." our editorial process Regina Bailey Updated August 08, 2019 B cells are white blood cells that protect the body against pathogens such as bacteria and viruses. Pathogens and foreign matter have associated molecular signals that identify them as antigens. B cells recognize these molecular signals and produce antibodies that are specific to the specific antigen. There are billions of B cells in the body. Unactivated B cells circulate in the blood until they come in contact with an antigen and become activated. Once activated, B cells produce the antibodies needed to fight against infection. B cells are necessary for adaptive or specific immunity, which focuses on the destruction of foreign invaders that have gotten past the bodies initial defenses. Adaptive immune responses are highly specific and provide long-lasting protection against the pathogens that elicit the response. B Cells and Antibodies B cells are a specific type of white blood cell called a lymphocyte. Other types of lymphocytes include T cells and natural killer cells. B cells develop from stem cells in bone marrow. They remain in the bone marrow until they become mature. Once they are fully developed, B cells are released into the blood where they travel to lymphatic organs. Mature B cells are capable of becoming activated and producing antibodies. Antibodies are specialized proteins that travel through the bloodstream and are found in bodily fluids. Antibodies recognize specific antigens by identifying certain areas on the surface of the antigen known as antigenic determinants. Once the specific antigenic determinant is recognized, the antibody will bind to the determinant. This binding of the antibody to the antigen identifies the antigen as a target to be destroyed by other immune cells, such as cytotoxic T cells. B Cell Activation On the surface of a B cell is a B cell receptor (BCR) protein. The BCR enables B cells to capture and bind to an antigen. Once bound, the antigen is internalized and digested by the B cell and certain molecules from the antigen are attached to another protein called a class II MHC protein. This antigen-class II MHC protein complex is then presented on the surface of the B cell. Most B cells are activated with the help of other immune cells. When cells such as macrophages and dendritic cells engulf and digest pathogens, they capture and present antigenic information to T cells. The T cells multiply and some differentiate into helper T cells. When a helper T cell comes in contact with the antigen-class II MHC protein complex on the B cell's surface, the helper T cell sends signals that activate the B cell. Activated B cells proliferate and can either develop into cells called plasma cells or into other cells called memory cells. Plasma B Cells These cells create antibodies that are specific to a specific antigen. The antibodies circulate in bodily fluids and blood serum until they bind to an antigen. Antibodies debilitate antigens until other immune cells can destroy them. It can take up to two weeks before plasma cells can generate enough antibodies to counteract a specific antigen. Once the infection is under control, antibody production decreases. Some activated B cells form memory cells. Memory B Cells This specified form of B cell enables the immune system to recognize antigens that the body has previously encountered. If the same type of antigen enters the body again, memory B cells direct a secondary immune response in which antibo