What is the function of B lymphocytes in the immune response?

B lymphocytes, or B cells, play a crucial role in the adaptive immune response primarily by producing antibodies. Antibodies are specialized proteins that bind to specific antigens, which are foreign molecules, typically found on pathogens like bacteria and viruses. When B cells encounter their specific antigen, they undergo a process called activation and differentiation, leading to the formation of plasma cells. These plasma cells are responsible for the synthesis and secretion of large amounts of antibodies into the bloodstream.

Once secreted, antibodies can neutralize pathogens directly by binding to them and preventing their entry into cells. They can also mark pathogens for destruction by other immune cells—a process known as opsonization—which enhances the ability of phagocytes to engulf and destroy the pathogens. Furthermore, antibodies can activate the complement system, which leads to the lysis of pathogens.

While other cell types and components of the immune system contribute significantly, such as T cells that directly kill infected cells and various factors that help enhance phagocytosis and stimulate inflammation, the unique and primary function of B cells in the immune response is the production of antibodies. This specialized role is fundamental to the development of long-lasting immunity and the effectiveness of vaccines.