Page 564 - Veterinary Immunology, 10th Edition

VetBooks.ir Other Mechanisms of Cellular

Cytotoxicity

T cell–mediated cytotoxicity is not the only way by which the
immune system can destroy abnormal cells (Table 18.1; Fig. 18.11).
For example, cells that possess the antibody receptors FcγRI or
FcγRII may bind to target cells or bacteria through specific

antibodies and then kill them. These cytotoxic cells may include
monocytes, eosinophils, neutrophils, B cells, and NK cells (Chapter
19). The mechanism of this antibody-dependent cell-mediated
cytotoxicity (ADCC) is unclear. However, neutrophils and

eosinophils probably release lethal oxidants and toxic granule
contents. ADCC is slower and less efficient than direct T cell–
mediated cytotoxicity, taking 6 to 18 hours to occur.

TABLE 18.1

Comparison of the Three Major Mechanisms of Cell-Mediated
Cytotoxicity

MHC Antigen
Cytotoxic Cells Time Mechanism
Restricted Specific
NK cells 24 hr NK-mediated No No
cytotoxicity
Normal lymphocytes or macrophages with FcγRIII with 6 hr ADCC activity No Yes
specific antibody
Primed T cells 10 T cell–mediated Yes Yes
min cytotoxicity

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