The branch of adaptive immunity that involves the activation of B cells and leads to the production of antibodies is called _____.

• A. Cellular
• B. Humoral
• C. Innate Immunity
• D. Adaptive Immunity

Answer: (B)

Humoral immunity is the arm of adaptive immunity that involves B cells and the production of antibodies. When a B cell recognizes its specific antigen and receives help from helper T cells, it proliferates and differentiates into plasma cells that secrete antibodies. These antibodies circulate in blood and lymph, bind to antigens on pathogens or toxins, neutralize them, prevent them from entering cells, and mark invaders for destruction by phagocytes or the complement system. Some B cells become memory B cells, providing a faster and stronger response if the same pathogen is encountered again. This is distinct from cellular immunity, which is driven by T cells that target infected body cells rather than free pathogens.