Which cell type is primarily responsible for humoral immunity?

• A. Cytotoxic T cells
• B. Natural killer cells
• C. B cells
• D. Helper T cells

Answer: (C)

Humoral immunity is the antibody-mediated branch of the adaptive immune response. It relies on B lymphocytes, which, after activation, differentiate into plasma cells that secrete antibodies into the bloodstream and lymph. These antibodies specifically recognize antigens, neutralize pathogens, and mark them for destruction through processes like opsonization and complement activation. Helper T cells help coordinate and amplify the B cell response, but the actual production of antibodies comes from B cells. Cytotoxic T cells target infected cells directly, and natural killer cells are part of the innate system, not antibody producers. So the cell type primarily responsible for humoral immunity is B cells.