Which of the following statements about humoral immunity is correct?
A. It is mounted by lymphocytes that have matured in the thymus.
B. It is a form of passive immunity produced by vaccination.
C. It defends against free pathogens with effector mechanisms such as neutralization, stimulation of phagocytosis, or complement activation.
D. It protects against pathogens that have invaded body cells as well as against cancer cells.
E. It requires recognition of class I MHC molecule-antigen complexes to activate its effector mechanism.
Answer: C. It defends against free pathogens with effector mechanisms such as neutralization, stimulation of phagocytosis, or complement activation.
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