Page 556 - Veterinary Immunology, 10th Edition

VetBooks.ir Cytotoxic T Cell Responses

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Once fully activated, CD8 T cells leave lymphoid organs and seek
out infected cells by themselves. When they recognize an antigen

expressed on another cell, the T cells will induce apoptosis and kill
their target (Fig. 18.6).

FIG. 18.6 Destruction of target cells by cytotoxic T cells. A,
Conjugation between a peritoneal exudate lymphocyte (the small
cell on the right) and a target cell. Note the lysosome-like bodies
(LY) and the nuclear fragmentation of the target cell (T). B, A
lymphocyte with the remains of a lysed target cell. (From Zagury D,
Bernard J, Thierness N, Feldman M and G Berke: Isolation and characterization of
individual functionally reactive cytotoxic T lymphocytes, conjugation, killing and
recycling at the single cell level, Eur J Immunol 5:881-822, 1975.)

The density of peptide-MHC complexes on a target cell required
to stimulate T cell cytotoxicity is much lower than that needed to

stimulate cytokine production. Thus T cell binding to a single
peptide-MHC complex may be sufficient to trigger killing, whereas
binding to 100 to 1000 complexes is required to stimulate cytokine

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