Which statement best describes humoral immunity?

• A. Relies on T cells to destroy infected cells
• B. Involves antibodies circulating in body fluids
• C. Provides the immediate nonspecific defense
• D. Is unrelated to fever responses

Answer: (B)

Humoral immunity is the branch of adaptive immunity that uses antibodies secreted by B cells to defend against pathogens that are outside cells. When a B cell with the right receptor meets its antigen and receives help from helper T cells, it becomes a plasma cell that floods body fluids like blood and lymph with antibodies. These antibodies bind to pathogens or toxins, neutralizing them directly or marking them for attack by other parts of the immune system. This is different from cell-mediated immunity, which relies on T cells to recognize and destroy infected cells, and from innate immunity, which provides immediate, nonspecific defense. Fever can accompany infections, but the defining feature of humoral immunity is the circulating antibodies in body fluids.