Final answer:
Plasma cells are activated B cells that produce antibodies as specific weapons to attach to antigens. These antibodies circulate in the blood and lymph, targeting pathogens for destruction.
Step-by-step explanation:
Plasma cells are activated B cells that secrete antibodies. Antibodies are large, Y-shaped proteins that recognize and bind to antigens. When plasma cells produce antibodies, they act as specific weapons that attach to antigens on pathogens, marking them for destruction by phagocytosis. The antibodies produced by plasma cells circulate in the blood and lymph, providing defense against pathogens throughout the body.