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 antibodies or memory B-cells that provide long-term immunity. When B-lymphocytes encounter an antigen, which is a substance that triggers an immune response, they become activated. This activation leads to the proliferation of B-cells and the production of specific antibodies tailored to the antigen. This process is essential for the body to remember and respond more effectively to future infections by the same pathogen.