B lymphocytes, or B cells, are a type of white blood cell that plays a crucial role in the immune system. They are responsible for producing antibodies, which are proteins that help identify and neutralize pathogens like bacteria and viruses. B cells originate in the bone marrow and can differentiate into plasma cells that secrete large amounts of antibodies when activated. When B cells encounter an antigen, which is a substance that triggers an immune response, they can also form memory B cells. These memory cells remain in the body long after an infection has cleared, allowing for a faster and more effective response if the same pathogen is encountered again in the future.