Immunity may be natural or acquired. Which of the following best describes acquired immunity?: (A) Increase in C-reactive protein (CRP), (B) Presence of natural killer (NK) cells, (C) Complement cascade, (D) Maternal transfer of antibody
Answer is D. Natural immunity is nonspecific. The description of natural immune functions described are not specific for a certain antigen. For example, certain proteins such as C-reactive protein (CRP) are acute-phase reactants. While elevated CRP is seen in infection, it is not disease-specific. Maternal transfer of antibody, however, is passive but still confers specific immunity. It is termed acquired immunity.