Which of the following statements about cell-mediated immunity (CMI) is NOT true?
A)Deficiencies in CMI result in susceptibility to infections by viruses and intracellular bacteria.
B)CMI can be adoptively transferred by injecting serum from one individual to another.
C)Delayed-type hypersensitivity (DTH) is not a protective response against intracellular bacteria such as Mycobacterium tuberculosis.
D)The principal form of CMI that protects against viral infections is mediated by CD8⁺ cytolytic T lymphocytes.
E)Phagocytes are essential in the effector phase of CMI responses to bacteria such as Listeria monocytogenes.

Question

Quizplus · Accepted Answer

The original definition of cell-mediated immunity (CMI), which is still valid, is protection against infection that can be transferred by T cells but not by serum. Serum is a cell-free fraction of blood that includes antibodies, and therefore serum transfer can provide passive humoral immunity. CMI is required for protection against microbes that can reside within cells and therefore are inaccessible to antibodies. These organisms include microbes that are phagocytosed and viruses that replicate in the cytoplasm. Immunodeficiency states in which CMI is impaired (e.g., AIDS) result in infections by viruses and intracellular bacteria or fungi. Delayed-type hypersensitivity (DTH), like all hypersensitivity reactions, causes tissue damage and disease, but not protection. It is true that DTH reactions involve the same cells and molecules as does CMI.

Which of the Following Statements About Cell-Mediated Immunity (CMI) Is