Which component of the immune system provides humoral immunity?

• A. T cells
• B. B cells and antibodies
• C. Neutrophils
• D. Macrophages

Answer: (B)

Humoral immunity is the antibody-mediated part of the immune response. It depends on B lymphocytes; when they encounter their specific antigen and receive signals from helper T cells, they differentiate into plasma cells that secrete antibodies into the blood and other body fluids. These antibodies bind to pathogens or toxins, neutralize them, flag them for destruction by other immune cells, and can activate the complement system. This contrasts with cellular (cell-mediated) immunity, which is driven by T cells that attack infected or abnormal cells. Neutrophils and macrophages are phagocytes involved in innate defenses rather than antibody production. So, B cells and the antibodies they produce are the components that provide humoral immunity.