B-Lymphocytes, or B-cells, are a type of white blood cell that play 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 antibodies when activated. When B-cells encounter a specific antigen, they undergo a process called clonal expansion, where they multiply and produce a large number of identical cells. Some of these cells become memory B-cells, which remain in the body to provide long-term immunity against future infections by the same pathogen.